Anatomy-of-a-Mine by freedomguide

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United States
Department
of Agriculture
Forest Service
Intermountain
Research Station                    OFA
                         MINE
General Technical
Report INT-GTR-35
Revised
February 1995


                           RM
                           FO
                      PROSPECT
                    PRODUCTION
Foreword                                                    This 1995 edition was funded by the Forest
                                                         Service's Mineralsand Geology ManagementStaff,
"Anatomy of a Mine"was first prepared in looseleaf       Washington, DC. The combined efforts of lnter-
form to aid Forest Service land managers and             mountain Regionand lntermountainResearchSta-
other administrators with mineral area responsi-         tion employees, and consultationwith other Forest
bilities. The material summarized legislation af-        Service Regions, in reviewing and updating the
fecting mining, defined mining terms, and dis-           material brings to the reader the most current
cussed basics of mineral exploration, develop-           mineralsmanagementinformation. We thank them
ment, and operation in the West. The goal then as        all for their continued efforts to foster better under-
now was to foster better understanding and com-          standing of basic legislation, terminology, and pro-
munication about minerals and forest and range           cesses used in the mining industry.
land surface values.
   The 1975 guide was written primarily by private
mining consultantsJames H. Bright and Anthony L.
Payne under direction of the Minerals and Energy         DENVER P. BURNS
Staff (now Minerals Area Management), Inter-             Acting Director
mountain Region, Forest Service. It quickly be-          lntermountain Research Station
came popular with land managers in many State
and Federal agencies. Planners, environmental-
ists, and mining industry personnelsought copies.
Educators from elementary through college levels         DALE N. BOSWORTH
have requested copies for classroom use.                 Regional Forester
   In 1977, a revised publication was issued in the      lntermountain Region
present format by the lntermountain Research
Station, with funding and compilation provided by
the Surface Environment and Mining Program. It           Abstract
was updated for another edition in 1983. Nearly            Reviews mining laws and regulations and their
20,000 copies of the various editions have been          application to mining inWestern States. Describes
distributed, and demand continues. A major use of        prospecting, exploration, mine development and
the publication is in training land managers.            operation, and reclamation factors.




         The use of trade or firm names in this publication is for reader information only,
         and does not imply endorsement by the U.S.   Department of Agriculture of any
         product or service.



                                        lntermountain Research Station
                                               324 25th Street
                                              Ogden, UT 84401
       OFA
     MINE
  PROSPECT
PRODUCTION
                                                                          CONTENTS
                                                                               Page                                                                                   Page
FOREWORD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .            ii      Electromagnetic . . . . . . . . . . . . . . . . . . . . . . . . 36
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . .                1       Electrical . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
MINING LAW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .            3       Radiometric . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
  Federal Laws . . . . . . . . . . . . . . . . . . . . . . . . . . . . .          3       Remote Sensing . . . . . . . . . . . . . . . . . . . . . . . . 37
    Claim Location . . . . . . . . . . . . . . . . . . . . . . . . .              4     Restudy of Old Mining Districts . . . . . . . . . . . 38
    Lode vs . Placer Claims . . . . . . . . . . . . . . . . . .                   5     Trenches, Pits, Overburden Drilling . . . . . . . . 39
    Extralateral Rights . . . . . . . . . . . . . . . . . . . . . .               5     Exploration Drilling . . . . . . . . . . . . . . . . . . . . . . . 40
    Tunnel Sites . . . . . . . . . . . . . . . . . . . . . . . . . . .            5       Hand Drilling . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
    Mill Sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .      6       Percussion Drilling . . . . . . . . . . . . . . . . . . . . . 41
    Claim Procedures . . . . . . . . . . . . . . . . . . . . . .                  6       Rotary Drilling . . . . . . . . . . . . . . . . . . . . . . . . . 41
  Pursuit of Discovery . . . . . . . . . . . . . . . . . . . . . .                7       Diamond Drilling . . . . . . . . . . . . . . . . . . . . . . . 42
  Protection Prior to Discovery . . . . . . . . . . . . . .                       8     Underground Exploration . . . . . . . . . . . . . . . . . 43
  Discovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .       9     Bulk Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
  Locatable Minerals . . . . . . . . . . . . . . . . . . . . . . .                9     Pilot Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
  Leasable Minerals . . . . . . . . . . . . . . . . . . . . . . . . 10                  Feasibility Studies . . . . . . . . . . . . . . . . . . . . . . . . 46
  Salable Minerals . . . . . . . . . . . . . . . . . . . . . . . . . . 10              DEVELOPMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
  Private Property . . . . . . . . . . . . . . . . . . . . . . . . . . 11               Drilling Large Deposits . . . . . . . . . . . . . . . . . . . 48
  State Laws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11           Drilling Small Deposits . . . . . . . . . . . . . . . . . . . 48
  Assessment Requirements . . . . . . . . . . . . . . . . 12                            Development Shafts and Adits . . . . . . . . . . . . 49
  Adverse Proceedings . . . . . . . . . . . . . . . . . . . . . 14                      Blocking Out Ore Underground . . . . . . . . . . . 49
  Rights of Claimants . . . . . . . . . . . . . . . . . . . . . . . 15                    Proven (Measured) Ore . . . . . . . . . . . . . . . . . 49
  Multiple Surface Use Act of 1955 . . . . . . . . . . 16                                 Probable (Indicated) Ore . . . . . . . . . . . . . . . . 50
  Occupancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16              Possible (Inferred) Ore . . . . . . . . . . . . . . . . . 50
  Trespass Limitations . . . . . . . . . . . . . . . . . . . . . . 17                   Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
  Federal and State Safety Requirements . . . . 18                                      Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
  Environmental Regulations . . . . . . . . . . . . . . . . 18                          Communications . . . . . . . . . . . . . . . . . . . . . . . . . 51
  Forest Service Regulations . . . . . . . . . . . . . . . . 18                         Site Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . 52
PROSPECTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21                    Mine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
  The Conventional Prospector . . . . . . . . . . . . . 22                                Mill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
  Amateur Prospectors . . . . . . . . . . . . . . . . . . . . . 23                        Townsite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
  Regional Mineral Exploration . . . . . . . . . . . . . . 23                           Postponement of Production . . . . . . . . . . . . . . 53
  Exploration Concepts . . . . . . . . . . . . . . . . . . . . . 24                    PRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
  Preliminary Evaluation of Exploration Results 25                                      Underground Mining Methods . . . . . . . . . . . . . 55
EXPLORATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26                    Open Stoping . . . . . . . . . . . . . . . . . . . . . . . . . . 55
  Planning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27           Shrinkage Stoping . . . . . . . . . . . . . . . . . . . . . . 55
    Personnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27              Cut and Fill Stoping . . . . . . . . . . . . . . . . . . . . 56
    Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27           Square-Set Stoping . . . . . . . . . . . . . . . . . . . . . 57
    Occupancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27                Block Caving . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
    Communications . . . . . . . . . . . . . . . . . . . . . . . 28                     Surface Mining Methods . . . . . . . . . . . . . . . . . . 59
    Property Adjustments . . . . . . . . . . . . . . . . . . . 28                         Placer Mining . . . . . . . . . . . . . . . . . . . . . . . . . . 59
    Contact With Federal Agencies . . . . . . . . . . 28                                  Glory Holing . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
  Geological Exploration Met hods . . . . . . . . . . . 28                                Open Pit Mining . . . . . . . . . . . . . . . . . . . . . . . . 61
    Criteria for Ore Recognition . . . . . . . . . . . . . 29                             Leaching Methods . . . . . . . . . . . . . . . . . . . . . . 62
  Geochemical Exploration Methods . . . . . . . . 32                                    Ore Dressing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
    Reconnaissance Geochemistry . . . . . . . . . . 32                                    Crushing and Concentration . . . . . . . . . . . . 63
    Rocks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32          Extractive Metallurgy . . . . . . . . . . . . . . . . . . . 64
    Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33      Wastes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
    Vegetation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35               Mine Wastes . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
  Geophysical Exploration Met hods . . . . . . . . . 35                                   Mill Wastes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
    Gravity ................................. 35                                          Miscellaneous Junk . . . . . . . . . . . . . . . . . . . . . 67
    Seismic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35          Roads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
    Magnetic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35          RECLAMATION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
   Western North America produces more met-             The era of the legendary mining engineer,
al and mineral products today than any other         who could go anywhere in the world and brisk-
region of similar size in the world. Beginning       ly size up the ore potential of any kind of miner-
with the forty-niner's discovery of gold, there      al property, passed during World War I. The
has been one surge of mining activity after an-      method of the mining engineer was to examine
other. Silver in the Civil War era, copper at the    and sample the partially developed ore depos-
turn of the century, potash, tungsten, phos-         its found by early gold and silver prospectors,
phate, uranium, beryllium, to name but a few,       to determine if other metals might be present,
have gained importance in turn as demand for         low grade ores might be profitably mined by
metal and mineral products increased and new         mechanized methods and treated by one of the
advances in technology were made.                   efficient new metallurgical processes, or the
   When contemplating the present mineral            property incorporated into a complex of mines,
production of the western United States, it is      all shipping to a large, efficient, centralized
difficult to imagine how undeveloped much of        smelter.
the region must have appeared to the early ex-          The modern explorationist goes back into
plorers. The natives had in their possession        areas investigated by the early prospectors
only a few trinkets of gold, silver, and copper,    and mining engineers, using new concepts of
and seemed to have little interest in, or know-     ore localization and techniques of search for
ledge of, minerals. The discovery of placer          mineral deposits that would have been of no
gold at Sutter's Mill at Coloma, California, in      interest to his predecessors. In the early years
January of 1848 was the first of many events        of mining, there was no market for most of the
that revealed the importance of the rich miner-      metals mined today. Transportation was inade
al resources of the West. The series of major       quate, mechanized equipment and technology
new mineral discoveries since the California        for development and treatment of the ores
gold rush seems paced almost as if the region       were lacking, and major capital was not avail-
were some sort of gigantic mineral warehouse        able for investment in large mine develop-
stocked with new commodities for use as they         ments and surface plants.
become needed.                                          The series of recent major discoveries of pre-
   Long gone are the days when mineral ex-          viously unknown deposits of such materials as
ploration consisted of probing outcrops of          uranium, beryllium, potash, and gold makes it
bold gold and silver veins. The list of minerals    very clear that the long-term prediction of fu-
required by industry today includes a majority      ture mineral discoveries is a most hazardous
of elements on the chemist's periodic chart,        occupation. It is not possible to determine that
and the variety of ore deposits in which they       an area is lacking in mineral potential when the
occur is so great that no one individual could      concept of the ore deposit containing it, the
possibly be competent to prospect for them all.     method of exploring for it, means of treatment,
No government specialist, academic author-          perhaps even the very use of it are totally un-
ity, or corporate expert is able to recognize the   known today. Therefore, the mineral explor-
surface expression of all ore types under all       ationist views public land as a reserve of poten-
conditions.                                         tial mineral resources in the very broadest
sense. He sees his task as the efficient future         authorities were seriously concerned because
exploration and discovery of ore deposits of            the United States lacked uranium ore, and the
sufficient number, size, and quality t o be com-        country's ability to defend itself and meet long-
petitively developed. In his view, the ultimate         term energy needs was in question. Incentives
logical extension of the idea that the Nation           were offered for uranium production, and ma-
should withdraw certain tracts of public land           jor discoveries such as the Mi Vida deposit in
for specific limited uses would require the res-        Utah by independent geologist Charles Steen
ervation of extensive areas for exploration and         motivated others, so that within 10 years the
and development of mineral resources.                   Nation had developed the largest, richest ura-
   Mineral values per acre may be immense in            nium ore reserves in the world. Uranium min-
any given mineralized area These values, wheth-         ing has grown to the point of being second only
er known or potential, should be considered             to copper in economic importance in metal
carefully in land use planning, particularly if         mining west of the Rocky Mountains.
withdrawals from mineral exploration and de-               There will be more pressure on public lands to
velopment are contemplated.                             produce minerals in the years to come. Many
   People within the mining industry have come          partially developed nations are beginning to
to view with skepticism any suggestion for tem-         look to their own future needs, and are no long-
porary withdrawal of mineral entry in a given           er a source of cheap, easily available, high qual-
area,where it is proposed that the land might           ity mineral raw materials. Established mineral-
later be opened to mining if the need becomes           producing countries are becoming ever more
great enough. They reason that the lead time            nationalistic, and several have recently revised
required to find, explore, and develop a pros-          mining laws and imposed new taxes upon min-
pect into a producing mine is such that the only        ing operations that have slowed or stopped
way to be sure of future mining operations is to        mineral exploration. Capital formerly invested
allow normal prospecting, exploration, and de-          in exploration in such areas is now being direct-
velopment over the widest possible area.When            ed to more politically favorable regions such as
poorly planned, hurried work is done in re-             the western United States.
sponse to crisis. This results in expensive ex-            The increase in domestic demand for miner-
ploration which is often not successful in de-          als progresses at an astonishing rate. More
veloping significant new mineral resources.             metal and mineral products have been used in
Also, great damage to the surface environment           the United States since World War II than were
may result.                                             used in the entire previous history of the world,
   Only a very small percentage of prospects            and demand increases each year. The sale of
develop into producing mines; authoritative             metal, minerals, and competitive products man-
estimates are in the range of 1 in 5,000 to 1 in        ufactured from them continue to increase in
10,000. The mineralized portions of the earth's         importance as a source of United States in-
crust are at fixed localities, and it is not possible   come overseas.
to move the economic concentration of miner-
                                                           Society unquestionably derives major bene-
al to a location where mining might conflict
                                                        fits from mineral production. To emphasize
less with other interests.
                                                        one commodity, the present major mining ac-
   Mining industry leaders believe that if the
                                                        tivity in the West centers upon the copper
search for minerals continues over broad ar-
                                                        mines of Arizona, New Mexico, Utah, Nevada,
eas, adequate new mineral resources can be
                                                        and Montana. Without these mines, copper
found and developed. If mineral exploration is
                                                        could not be produced in large quantities and at
severely restricted, confined to much smaller
                                                        low cost, allowing its general use in mass produc-
areas, or if unreasonable burdens are placed
                                                        tion of electrical power, transportation, and other
on mining itself making investment unattrac-
                                                        conveniences enjoyed by everyone today. Sim-
tive, they feel that the number of new mineral
                                                        ilar benefits could be cited in the case of other
finds will dwindle, perhaps to the point of major
                                                        minerals such as lead, zinc, silver, gold, iron,
damage to the economy and the ability of the
                                                        coal, tungsten, and uranium. A healthy mining
United States to provide for itself.
                                                        industry is important to the economy of the
 As an example of the unpredictable course of           United States. The future need for minerals
mineral development, 25 years ago Government            cannot be expected to diminish unless there is
a major turn downward in the standard of living    years contemplate closure of public land to
presently enjoyed in the United States. There is   mining. Mining has always been an authorized
no doubt that the potential for future disovery    use of most National Forest land in the West.
of major new mineral resources exists on pub-      The language of the original legislation cre-
lic land.                                          ating and authorizing the National Forests set
                                                   forth the rights of a mineral locator as essen-
   Some mining people and resource man-            tially the same as those of a person who locates
agers think that the present mining laws of the    a claim on other public land. The rights of the
United States may soon be changed or modi-         mineral claimant to explore and develop avalid
fied. However, it should be noted that none of     claim on public lands open to mineral entry are
the laws considered by Congress in recent          clearly recognized.




                                                                   MINING LAW                         I
  The body of mining law that authorizes and         A cornerstone of the early California Mining
controls prospecting, claim procedures, leas-      Law was that the discoverer obtained the right
ing, development, and extraction of minerals on    to his discovery. The early day custom was that
public lands includes Federal and State laws,      a claim did not become property until mineral
regulations issued by administering agencies       was discovered and perfected by development.
based upon those laws, and court decisions         This was the pattern for later law.
that have established precedents for settling        An 1866 mining law confirmed existing min-
disputes. Rules established by organized min-      ing claims and contained the declaration that
ing districts, envisioned as important in early    the minerals on public land were open to ex-
Federal law, have little significance today. The   ploration by all citizens of the United States.
organized districts have been gradually elimi-     The locator was given legal protection for his
nated in most western States.                      claim, and a system was devised by which a
                                                   lode locator might acquire title by patenting. In
                                                   1870 the Placer Act amended the 1866 law to
           Federal Laws                            provide a method of patenting placer claims.
                                                   These several acts facilitated the development
   Acquisition of mining claims on public land     of mineral resources of the western States and
is a right granted by the United States Mining     territories.
Law of 1872. This law, passed by Congress on          In 1872 the Acts of 1866 and 1870 were re-
May 10, 1872, continued a policy of opening        passed by Congress as a single statute entitled
mineral lands to exploration. The United States    the United States Mining Law of 1872. The ac-
Mining Law of I872 expresses the general sys-      quisition of mining rights on large amounts of
tem of acquiring mining claims that was form-      public land in the West is, for the most part, still
ed in California and Nevada between 1848 and       governed by this law. The principal exceptions
1866. Until 1866 there was a Federal policy of     are the Mineral Leasing Act of 1920, which
benign neglect with the mineral claim system       made certain nonmetalliferous minerals exclu-
in use in the West.                                sively leasable and not open to acquisition by
claim staking, the Materials Act of 1947 that de-              side of the middle of the vein at the surface.
fined a group of salable minerals; the Multiple                Surface end lines must be parallel.
Mineral Use Act of 1954 that provided for multi-                  2. Upon completing the lode location, the
ple mineral development of the same tracts of                  locator has the exclusive right of possession
public lands; the Multiple Surface Use Mining                  and enjoyment of all (a) surface included with-
Act of July 23, 1955, that withdrew common                     in the lines of the location for mining purposes;
varieties from mineral entry; and a section of                 and (b) all veins, lodes, or ledges throughout
the Federal Land Policy and Management Act                     their entire depth if t he top or apex lies inside of
of I976 that redefines claim recording proce-                  the surface lines extended downward vertical-
dures and provides for abandonment if the pro-                 ly, even though such veins may extend outside
cedures are not followed.                                      the vertical side lines of the surface location.
                                                                  3. Placer claims located by a single individ-
              Claim Location                                   ual and based upon a single discovery are lim-
  The principal provisions of the 1872 statute                 ited to 20 acres. An association of individuals
are:                                                           may locate up to 160 acres on each discovery.
   1. After discovery of a lode or vein, a mining                 4. Both placer and lode locators are requir-
claim may be located on a plot of land not ex-                 ed to perform $100 worth of development work
ceeding 1,500 feet in length along the lode or                 per claim annually in order to hold their claims
vein and 300 feet on each side of the middle of                against subsequent locators.
such vein at the surface (fig. 1). Local mining                   5. There is provision for acquiring 5-acre
district rules or State laws may limit the width               claims of nonmineral land for mill site pur-
of such claims t o not less than 25 feet on each               poses.


     Examp
     --l e s of c l a i m m o n u m e n t s
                m




                                                                                                     luments
                                                                                                     1 states)




                                              Figure 1.--Lode mining claim.


                                                           4
  6. The section commonly referred to as the              legal subdivisions. All of the persons in an as-
Tunnel Site Act gives an individual the right to          sociation must be active participants in the
prospect a maximum of 3,000 feet into a hill-             venture. The rights of a "dummy locator" may
side, acquiring a prior right to all theretofore          be invalid, if he fails to actively assert the rights
unknown veins and lodes cut by the tunnel;                of a principal in the location. Corporations are
however, no surface rights are attached.                  considered to be a single person. There is no
  The United States Mining Law of 1872 does               limit to the number of placer claims that may be
not sanction the disposal or use of public lands          located by an individual or association.
for purposes unrelated t o mining.
                                                                     Extralateral Rights
        Lode vs. Placer Claims
                                                             The locator of a valid lode mining claim ac-
   The mining location laws authorize two main            quires the right to mine all the veins and ledges
types of claims--lode and placer--depending               throughout their entire depth, the tops or apex-
on the character of the deposit. Lode claims              es of which lie inside of the claim surface lines
are staked on veins or lodes of quartz or other           (fig. 2). Such veins or ledges may depart from a
rock in place bearing gold, silver, cinnabar,             perpendicular in their course downward so as
lead, tin, copper, or other valuable deposits.            to extend outside vertical, downward exten-
Placer claims are staked on all forms of depos-           sions of the sidelines of the claim. Rights of the
it, excepting veins of quartz, or other rock in           claim holder to mine the deposits after they
place.                                                    leave the vertical claim lines underground are
   The locator must decide into which category            known as his extralateral rights.
his deposit falls and stake a lode or placer                 Extralateral rights apply only to lode claims
claim as appropriate.                                     w i t h parallel end        lines and usually
   In the United States Mining Law of 1872,               do not extend under adjacent private land.
Congress drew a distinction between the tradi-            Lawsuits over extralateral rights were very
tional gold placer composed of alluvial materi-           common at one time, but today such disputes
al along streambeds and the vein or lode found            usually are settled privately.
in solid rock. In many modern cases the choice
is difficult as many deposits do not clearly fall
into either category.
                                                                          Tunnel Sites
   A lode is frequently considered as a zone or              The law provides for tunnel sites where a
belt of mineralized rock clearly separated from           horizontal excavation (adit) is made to dis-
neighboring nonmineralized rock.                          cover lodes and veins not appearing at the sur-
   Placers are superficial deposits washed                face. The owners of such tunnels gain the right
down from avein or lode occupying the beds of             of possession of any previously unknown
ancient rivers, or deposits of valuable minerals          veins or lodes discovered along the 3,000-foot
found in particles of alluvium in beds of active          distance between the portal and face of the
streams.                                                  tunnel.
   These definitions emphasize the present                   A tunnel site conveys no surface rights and
form of the deposit more than its origin, so that         the right of possession of avein discovered in a
a deposit bounded on either side by rock in               tunnel cannot be maintained unless the owner
place is likely to be considered a lode. If the ore       makes a lode location of the vein on the sur-
is on top of the ground and has no cover except           face. Discontinuing work for 6 months consti-
a thin veneer of soil, it is likely to be a placer. I n   tutes abandonment of a tunnel site.
the case of a dispute the courts tend to find in             A monument must be placed at the portal of
favor of the first locator.                               the tunnel naming the locator, stating the pro-
   A placer claim can be no larger than 20 acres          posed direction of the tunnel, its height and
for an individual, with associations of up to             width, and the course and distance from the
eight persons locating multiple claims of 20              portal to a permanent object in thevicinity. The
acres per person up to 160 acres. A placer loca-          boundary lines of the tunnel site must be estab-
tion does not establish rights to any lodes with-         lished by stakes placed along the 3,000-foot
in its boundaries. Placer locations must con-             length of the tunnel line. Tunnel sites are un-
form as nearly as practicable t o rectangular             common today.
                             Figure 2.--Extralateral rights of a lode mining claim.



                 Mill Sites                                 copy of a location notice must be placed at the
                                                            point of discovery and the location notice must
   A 5-acre plot of nonmineral land may be
                                                            be recorded with the recorder of the county in
staked as a mill site. The land need not be con-
                                                            which the claim is situated. The Federal Land
tiguous to the claim that will produce the ore
                                                            Policy and Management Act of 1976 requires
for the mill. Mill sites are monumented in the
                                                            that claim location documents also be filed
same manner as lode claims. No assessment
                                                            with appropriate offices of the Bureau of Land
work is required; but the mill site must be used
                                                            Management.
for mining and milling purposes.
                                                              Historically, mining claims have been mark-
                                                            ed or staked in a variety of ways. Claim corners
          Claim Procedures                                  and discovery points have been marked on the
   Under the United States Mining Law of 1872,              ground by rock monuments or cairns, trimmed
land is claimed for minerals by distinctly mark-            and blazed trees, or iron posts embedded in
ing the location on the ground so that its                  soil, rock, or concrete. The most common
boundaries can be readily traced and making a               markers, however, are 4-by-4 wood posts.
record of the name or names of the locators,                  It is essential that the discovery be made and
date of location, and a description of the claim            that the location monument and notice be on
or claims located by reference to some natural              public land open to mineral entry, otherwise
object or permanent monument that will identi-              the entire claim is invalid. Portions of a youn-
fy the claim. In addition, State law requires the           ger lode location may overlap older locations
monumentation of claims by cornerposts, and                 and claim boundary monuments may be
in some cases, side and end centerposts. A                  placed on land already claimed in order to
square the claim or to take advantage of an ex-        Copies of the mining law and regulations in a
tralateral right not held in apex by previous       form usable by prospectors, geologists, and
locators. The location monument is erected at       Federal employees can be obtained in Title 43
some point along the centerline inside the          of Code of Federal Regulations and in Title 30
claim. Less than 300 feet on either side of the     of the U.S. Code Annotated. The pertinent por-
centerline and less than 1,500 feet along the       tions of the 1872 law are published as a bro-
centerline may be claimed, but the claim can        chure by the U.S. Department of Interior,
never exceed 600 by 1,500 feet in size.             Bureau of Land Management, entitled Regula-
   All unappropriated Federal lands that have       tions Pertaining to Mining Claims Under the
not been withdrawn from mineral entry are           General Mining Laws of 1872, Multiple Use,
open to locations of mining claims. Appro-          and Special Disposal Provisions.
priated public lands--those original public
lands which are covered by an entry, including
mining claims, patent certification, or other            Pursuit of Discovery
evidence of land disposal; or which are within a       In past years prospecting was limited to sur-
reservation, contain improvements construct-        face outcrops where discovery was easily
ed with Federal funds or are covered by certain     made with limited equipment. Factors such as
classes of leases--are not open t o mineral         the ever-increasing demands for new mineral
entry. Lands covered by mining claims validly       resources, the economic incentives to produce
maintained by another person are not subject        minerals, and the exhaustion of many known
to location.                                        deposits make it necessary to intensify the
  Mining claims can be located in Alaska,           search for new mineral deposits and to explore
Arkansas, Arizona, California, Colorado,            to considerable depths below the ground
                                                    surface.
Florida, Idaho, Louisiana, Mississippi,
Montana, Nebraska, Nevada, New Mexico,                 Science and technology have provided new
                                                    methods, techniques, and instruments to aid in
North Dakota, Oregon, South Dakota, Utah,
                                                    exploration. Mining com pan ies have risked
Washington, and Wyoming.
                                                    millions of dollars in mineral exploration and
   Land in National Monuments or National           research. This has trained and provided
Parks, unless specifically authorized by law,       experience for mineral explorationists in the
Indian reservations, and acquired lands are not     art and science of ore finding. These
open for location. The claim locator must be a      advancements in ore finding capability open a
United States citizen or must have declared an      new dimension n o t available t o most.
intention to become a citizen. A domestic corp-     prospectors. The old-fashioned prospector
oration is considered to be a citizen, regardless   can find only what can be seen at the surface,
of the nationality of its stockholders. Employ-     and normally cannot afford the sophisticated
ees of the Departments of the Interior and          methods used by the mining companies.
Agriculture are restricted in some ways from           Exploratory work is necessary, in many
staking claims. A minor competent to acquire        instances, to perfect a discovery. The general
and hold interests in land under State law is a     mining laws are presently interpreted as
qualified locator.                                  extending an express invitation to enter upon
  The 1872 law specifically requires discovery      the land and explore and, upon discovery, to
of a valuable mineral deposit within the limits     claim by location with the promise of full
of the claim prior to locating a mining claim.      reward. The prospector who enters upon
Modern day mineral deposits are most often          vacant public land, peacefully and in good
found at great depth and the actual discovery       faith, is not a trespasser, but is a licensee or a
of mineral in place commonly occurs in a drill      tenant at will. This right to enter is a statutory
hole after considerable exploration work. The       right. A mineral discovery cannot be made
prospector or geologist finds geological,geo-       without the right of entry and the time
physical, or geochemical indications of             explore.
mineralization long before the drilling phase of       Excavations are a necessary part
the program encounters the discovery of             exploration for minerals. This necessity
mineral in place.                                   excavate is not necessarily tantamount
removal and sale of the excavated minerals.           A lode discovery will not suffice for a placer
The prospector seeks only to make a discovery       claim nor will a pacer discovery suffice for a
by the use of such an .excavation. In some          lode claim, and the discovery must be within
cases it is necessary to sell extracted minerals    the limits of the claim.
to meet the marketability test of the valuable
mineral deposit.
   Discovery of a valuable mineral deposit is             Protection Prior to
essential in creating valid rights to a claim and
in obtaining a patent.                                        Discovery
   Because the discovery is the foundation of          A person actively exploring a prospect desir-
title to a mining claim, discovery must be          es protection against another locator on the
pursued diligently by a bona fide claimant.         land that he is exploring, for the time neces-
Normally, to the locator, the sequence of           sary to discover minerals in place.
events is immaterial. Discovery may precede            The courts have recognized this problem
the location of a claim or may follow the act of    and arrived at the doctrine of pedis possessio
location; however, the actual time of discovery     to provide protection to the modern bona fide
is important in that it establishes priority        prospector.
between claimants and with the Government              Under the pedis possessio doctrine, a claim-
when there is conflict. Priority of discovery       ant who has peacefully and in good faith stak-
gives priority of rights.                           ed claims in search of valuable minerals, may
   When two locators are in possession of           exclusively hold the claims while he is diligent-
overlapping claims before discovery, a race         ly working against others having no better right
develops between the locators t o make a            than he, so long as he retains a continuous ex-
discovery first and the first discoverer obtains    clusive occupancy and in good faith works to-
priority of rights. The rights of a locator         ward making a discovery. During the period
actually begin on the date of discovery of a        that the doctrine is operative in a particular
valuable mineral deposit on a claim. This is true   situation, the claimant must be actively work-
whether or not the required location work           ing toward making a discovery by digging or
precedes or follows discovery. The need for         drilling. Making preparations for digging or
secrecy in a new discovery can be easily seen in    drilling may not besufficient unless the prepar-
a case of probable competition from a rival         atory activity directly precedes the actual dig-
capable of staking conflicting claims. There is     ging or drilling.
no substitute for discovery on a mining claim.         Whether or not a prospector, geologist, or
Length of time held and amount of money or          mining company can successfully assert rights
effort consumed in working on a claim does          of pedis possessio may vary in each particular
not dispense with the need for discovery.           case. To claim the rights there must be actual
   Where the issue of discovery is raised in a      physical possession of all the ground, diligent
controversy with the Federal Government, the        bona fide work directed toward making a dis-
finding of small amounts of subeconomic             covery, and others must be excluded.
mineral in sufficient quantity to encourage or         It is common exploration practice to locate a
induce further prospecting and exploration is       large block of claims over and around an area
not sufficient for a discovery. The actual          where it is suspected that deposits of valuable
mineral deposit must be disclosed and               minerals may occur. The locator of such
available for sampling by some means.               blocks is well advised to maintain exclusive
Geological inference or opinion, no matter          possession and to pursue a discovery on each
how strong, will not substitute for the actual      claim.
exposure of mineral. Hope, belief, or expecta-         This possession or occupancy of the claims
tion will not sustain a discovery.                  must be more than mere presence. Geophysi-
   There must be physical exposure of valuable      cal testing and geochemical work, unless fol-
mineral in surface outcroppings, pits, shafts, or   lowed immediately by drilling, may not be suf-
drill hole samples to demonstrate the discov-       ficient. However, the requirement of physical
ery. Drill core or cuttings will usually be ac-     occupancy is usually satisfied by work in pro-
cepted.                                             gress. The exclusion of others requires posi-
tive action. Rights are lost if an adverse claim-       There continues to be a contest between the
ant is permitted to enter the property peace-        prudent man test and its extension -- the
fully. Pedis possessio protects against forcible     marketability test. Every locator should be pre-
entry. Thus it is necessary to deny entry to the     pared to defend his discovery under the stand-
intruding party.                                     ards of the marketability test. If a contest devel-
   If a confrontation occurs, and force is used      ops, the claim holder may be required to prove
by the entering party, the denial of entry need      marketability in today's market.
not be successful. The claimant or his agent            In considering these definitions of discov-
simply yields to force, and then goes to his         ery, certain rules must be kept in mind. The
legal remedy. The claimant should make no            deposit discovered must be a valuable mineral
statements indicating consent to trespass. In a      deposit. This commonly means an assay or test
land rush situation, a claim block should be         of some kind must be made to determine the
patrolled to deny entry to other than author-        quantity and quality of metal or commodity in
ized public officials. Proposed new changes in       the discovery. The size of the deposit and the
the Federal mining laws provide for explora-         probable cost of production are also considered.
tion claims to cover a large area during the per-       The immediate effect of a valid discovery is
iod prior to the discovery of valuable mineral in    to remove the land upon which the discovery
place. This could remedy some of the short-          has been made from the unappropriated public
comings of the 1872 Mining Law.                      lands.
                                                        The rules for determining what is a discovery
                                                     of valuable mineral may vary according to the
                                                     parties and interests involved. The tests are
               Discovery                             quite different in a contest between two ad-
   What is a discovery? The Federal statutes         verse claimants than the tests used by the U.S.
that require discovery do not define the term,       Government in a contest with a claimant. The
 and the definition of discovery under the           United States, by appropriate methods, may
 United States Mining Law of 1872 continues to       question the validity of a claim at any time and,
 be a subject of controversy. One basic stand-       in the absence of a discovery, may terminate
 ard for discovery has been the prudent-man          the prospector's possession of a particular
test, which states that the requirements of          claim by adjudication. The claimant, however
discovery have been met when minerals have           may locate another claim on the general site,
 been found and there is evidence that a person      if he is acting in good faith.
of ordinary prudence would be justified in the
further expenditure of labor and money, with a
 reasonable prospect of success in developing              Locatable Minerals
a valuable mine.                                        Whatever is recognized as a valuable mineral
   The test is not whether the individual            by standard authorities, whether metallic or
claimant feels he is justified in further expendi-   other substance, when found on public land
ture, but whether a hypothetical "reasonable"        open to mineral entry in quality and quantity
man would be so justified, and whether a             sufficient to render a claim valuable on
profitable mining venture is probable.               account of the mineral content, is considered a
   In 1933, the U.S. Department of the Interior      locatable mineral under the United States
formulated the marketability test as a standard.     Mining Law of 1872. Specifically excluded
The marketability test states that the mineral       from location are the leasable minerals,
locator or applicant, to justify his possession of   c o m m o n varieties, and salable minerals
a location, must show b y reason of                  described in the next two sections.
accessibility, development, p r o x i m i t y t o       Every valuable mineral deposit that is not
market, existence of present demand, and             excluded by special legislation is a locatable
other factors that the deposit is of such value      mineral. The United States Mining Law of I872
that it can be mined, removed, and disposed          specifically mentions rock in place bearing
of at a profit.                                      gold, silver, cinnabar, lead, tin, copper, or other
   The marketability test focuses on the             valuable deposits. As a general rule, all
economic value at the present time.                  valuable metallic mineral deposits are
locatable plus a large group of nonmetallic          to the highest bidder, either by sealed bid or
substances which have been determined to be           at public auction. Leases issued in this manner
locatable by either the Department of the            are termed competitive leases. Regulations
Interior, a Federal or State court, or legislation    pertaining to the leasing of minerals other than
by Congress. Some of the nonmetallic                 oil and gas can be obtained in a Bureau of Land
minerals in this group are borax, feldspar,           Management Circular or in Title 43 of the Code
fluorspar, and gypsum.                               of Federal Regulations.
   If a prospector, geologist, or land agency            Public lands that passed from Federal
representative has any doubts about the              ownership through acts of Congress or
locatable classification of a mineral deposit, he     disposal laws and were later reacquired by the
should consult a mineral expert on this point.        United States are known as acquired lands.
                                                      Minerals subject to location on other lands
                                                      must be leased on acquired lands.
       Leasable Minerals                                The royalty rates for each lease are set by
   The first major change in the United States       the U.S. Department of the Interior and may
Mining Law of 1872 came with the passage of          be obtained from BLM offices. For all miner-
the Mineral Leasing Act of 1920. Certain             als in the same general area, royalties are
minerals were withdrawn from location and            usually the same. Royalties for the same
were placed under the Leasing Act which              minerals may be different i n various areas of
provides for their development t h r o u g h         the United States.
prospecting permits and leases. No permanent            The Multiple Mineral Use Act of 1954 allows
rights are acquired from the U.S. Government,        land that is leased for one commodity to be
only the right to explore for and mine the           claimed to cover minerals not in the leasable
specific minerals covered by the lease or            category. In some cases this can be important
permit.                                              where locatable minerals are found in an oil
   The 1920 Act, as amended from time to time,       and gas lease area.
places the following minerals under the leasing
law: oil, gas, coal, oilshale, sodium, potassium,            Salable Minerals
phosphate, native asphalt, solid or semisolid           The Materials Act of 1947, as amended,
bitumen, bituminous rock, oil-impregnated            removes petrified wood, common varieties of
rock or sand, and sulfur in Louisiana and New        sand, stone, gravel, pumice, pumicite, cinders,
Mexico.                                              and some clay from location and leasing.
   In general, to hold a lease, the miner is         These materials may be acquired by purchase
required to pay an annual rental in advance, to      only and are referred to as salable minerals.
pay a royalty to the Government on all material         Sales are handled through the agency
removed and sold, and to comply with any             administering the land upon the request of an
other provisions written into the lease.             interested party or upon the request of an
  The acquisition of mineral deposits by a           authorized official. Sales are by competitive
lease from the Bureau of Land Management is          bidding if there is more than one interested
very different from the location of a valid claim    party, otherwise a sale is negotiated by the
on a mineral discovery. Areas involved in            authorized officer after the materials are
leases are large compared to individual mining       appraised.
claims because of the nature of the occurrence          The sale of minerals does not limit the right
of leasable minerals. Filing fees and yearly land    of the U.S. Government to use the surface and
rental fees are collected in advance, and bonds      to issue permits and licences that do not
in varying amounts are required before the           interfere with the purchaser's production of
issuance of either a prospecting permit or a         minerals. The land must be reclaimed as
lease.                                               required by the sale contract or by law when
   In areas in which leasable mineral deposits       mining is completed.
are not known to occur, minerals can be leased          A mining claimant risks prosecution for
by a noncompetitive procedure. In areas in           trespass and may be liable for damages if he
which leasable mineral deposits are known to         removes salable materials from an unpatented
occur in marketable quantities, leases are issued    mining claim.
         Private Property                              Normally, the mining company attempts to
                                                       obtain a lease with option to purchase from the
    It is not uncommon for minerals beneath pri-       owner.
vate property to be owned by someone other
than the surface owner or by the Government.
    Parcels of land that passed from the public
                                                                     State Laws
domain into private ownership prior to the                 The United States Mining Law of 1872 did
Stock Raising Homestead Act of December 29,             not preempt the field, and State laws are
 1916, were classified as nonmineral and the            permitted to elaborate on some aspects of
minerals that might be under these lands                mining law not covered specifically by the
passed to the fee owners of the surface. This           Federal act.
1916 Act eliminated any problems of mineral                State statutes deal primarily with location
versus nonmineral lands by providing for the           procedures, some aspects of assessment re-
reservation to the United States of all minerals       quirements, and the time method for filing
in every patent under this Act. Thus, most             documents. Most western States require post-
lands patented under the various homestead              ing of the notice of location on the land, which
acts from the public domain after 1916 are              is not required by Federal law. The information
open to mineral entry under the United States           required on the notice varies from State to
Mining Law of 1872.                                    State, and contains substantially the same
    There are many laws under which the                 information as the recorded certificate.
original title to land could be obtained, and it is        Nearly all States require location work, al-
necessary to check the document in the land            though the Federal law does not. Although
records to determine the law under which the           location work is intended to disclose the evi-
title was granted.                                     dence of discovery, it may or may not result in
    Disposals under other laws both before and         a discovery. Location work is sometimes
after the Stock Raising Homestead Act of 1916          erroneously referred to as discovery work.
often reserved minerals to the Government.                 All States require corner monuments. End-
The Secretary of the Interior has never issued         center and side-center monuments may or
regulations to dispose of these reserved               may not be required and the size and character
minerals.                                              of these monuments varies from State t o State.
                                                           All records of unpatented mining claims are
    It is necessary for the miner to pay the private   kept in the county courthouse of the county in
surface owner for damage to the surface                which the claim is located. Under provisions
caused by prospecting, mineral development,            of the Federal Land Policy and Management
and mining. This is commonly done by                   Act of 1976, similar documents will have to be
arranging for a bond through the Bureau of             filed with appropriate Bureau of Land Manage-
Land Management as security for damage to              ment offices.
the surface, or by entering into a contract with           When the United States Mining Law of 1872
the surface owner.                                     was passed, most western land was
   Sections 5 and 6 of the Taylor Grazing Act of       unsurveyed. In some western States there is
June 28, 1934, as amended, provided that the           still unsurveyed land. In many cases the
rights of the miner were not t o be restricted in      descriptions of mining claims are so vague that
prospecting, locating, developing, mining,             they can properly be considered a floating
entering, or patenting under applicable laws           claim block. For unscrupulous claimants this
any mineral deposits found on lands leased for         type of claim block may have the utilitarian
grazing. The grazing lease holder cannot               value of being moved over any new discovery
restrict proper and lawful ingress or egress for       in the vicinity. The floating claim block can be
prospecting purposes.                                  moved anyplace that the claimant desires by
   Minerals that are owned in fee simple by the        moving the claim posts and thus predate
surface owner or that have been reserved in            claims made by the discoverer. It is normally
private ownership separately from the surface          possible to contest such action, but the
are not open for prospecting, development, or          claimant may hold out for a considerable cash
mining without permission from the owner.              payment for his nuisance value. Many
attorneys w i l l advise t h e major m i n i n g        on the 1st day of September succeeding the
company to pay rather than fight, in order to           date of location of such claim ....
get on with exploration.
                                                        By Act of February 11, 1875, the following
   State mining laws in some cases require a
                                                      provision was added to the United States
map filed with the county recorder and
                                                      Mining Law of 1872:
perhaps a payment as well in lieu of location
work. In Nevada, the county uses the payment            ...Where a person or company has or may
t o compile a master c l a i m map, thus                run a tunnel for the purposes of developing
eliminating floating claims. Any extra fee              a lode or lodes, owned by said person or
money provides an income to the county for              company, the money so expended in said
general use.                                            tunnel shall be taken and considered as ex-
   Most mining legislation does not vary drasti-        pended on said lode or lodes, whether locat-
cally from State to State; however, there is            ed prior t o or since May 10, 1872; and such
enough variation that an element of confusion           person or company shall not be required to
and uncertainty pervades the State mining               perform work on the surface of said lode or
laws and a prospector or geologist must always          lodes in order to hold the same as required
carefully examine the law, particularly with            by this section ....
reference t o location and assessment
                                                        The most recent Federal legislation was
procedures.
                                                      enacted on September 2, 1958, and provides:
                                                        ...The term labor, as used in the third sen-
Assessment Requirements                                 tence of section 2324 of the Revised Statutes
                                                        (30 U.S.C. 28), shall include, without being
  The annual labor or improvements required             limited to, geological, geochemical and geo-
by the United States Mining Law of 1872 on an           physical surveys conducted by qualified ex-
unpatented claim is commonly referred to as             perts and verified by a detailed report filed in
assessment work. The general purpose of this            the county office in which the claim is locat-
work is to assure good faith and diligence and          ed which sets forth fully (a) the location of
to prevent a claimant from holding claims               the work performed in relation to the point of
without working the ground, thus preventing             discovery and boundaries of the claim, (b)
others from making entry.                               the nature, extent, and cost thereof, (c) the
  The pertinent provisions of the United States         basic findings therefrom, and (d) the name,
Mining Law of 1872 require assessment work              address, and professional background o f t he
as follows:                                             person or persons conducting the work.
  ...On each claim located after the 10th day of        Such surveys, however, may not be applied
  May, 1872, and until a patent has been issued         as labor for more than two consecutive years
  therefore, not less than $100 worth of labor          or for more than a total of five years on any
  shall be performed or improvements made               one mining claim, and each survey shall be
  during each year ...; but where such claims           nonrepetitive of any previous survey on the
  are held in common, such expenditure may              same claim ....
  be made upon any one claim; and upon a
  failure to comply with these conditions, the         The regulations as stated in Title 43 of the
  claim or mine upon which such failure oc-           Code of Federal Regulations, provide that:
  curred shall be open to relocation in the
                                                          (a) The term geological surveys means
  same manner as if no location of the same
                                                        surveys on the ground for mineral deposits
  had ever been made, provided that the origi-
                                                        by the proper application of the principles
  nal locators, their heirs, assigns, or legal rep-
                                                        and techniques of the science of geology as
  resentatives have not resumed work upon
                                                        they relate to the search for and discovery of
  the claim after failure and before such loca-
                                                        mineral deposits;
  tion .... The period within which the work re-
  quired to be done annually on all unpatent-             (b) The term geochemical surveys means
  ed mineral claims located since May 10,               surveys on the ground for mineral deposits
  1872, shall commence at 12 o'clock meridian           by the proper application of the principles
  and techniques of the science of chemistry           a community of interest if more than one claim
  as they relate to the search for and discovery       owner is involved. There are no rules that
  of mineral deposits;                                 completely cover the grouping of claims. The
                                                       circumstances in each case can be important.
    (c) The term geophysical surveys means
                                                          As a practical matter, many claim holders do
  surveys on the ground for mineral deposits
                                                       little or no assessment work on their claims and
  through the employment of generally recog-
                                                       file questionable proof of labor statements. In
  nized equipment and methods for measuring
                                                       some circumstances this may constitute
  physical differences between rock types or
                                                       perjury.
  discontinuities in geological formations; and
                                                           If there is a contest over the performance of
    (d) The term qualified expert means an             assessment work, the burden of proof
  individual qualified by education or experi-         concerning the performance generally is on
  ence to conduct geological, geochemical or          the party contending that the required work
  geophysical surveys, as the case may be.            was not done. As a general rule, in court cases
                                                      where a second locator attempts to relocate
                                                      the claim of the original locator who has
    In most States, filing of proof of labor in the
                                                       allegedly failed to perform the required
county records is required by State law within a
                                                      assessment work, most decisions tend to
 limited time period.
                                                       protect the original locator where it appears
   The question of what can qualify for assess-
                                                      that he has acted in good faith. The courts
ment work is not always easy to answer. It is
                                                      generally do not substitute their judgement for
necessary to remember that it is $100 worth of
                                                      that of the miner i f the work tends t o develop
labor and improvements. The work must have a
value of $100, not necessarily cost $100.             the claim and facilitate the extraction of ore.
Geological, geochemical, and geophysical                  The absence of an assessment work affidavit
surveys, some road work, tunneling, digging           in the county records may encourage a new
pits, cuts or trenches, or excavations, and           claimant interested in the ground to locate new
drilling which tends to develop the mineral           claims. The failure by the original locator to file
deposit qualify as assessment work.The intent         the proof of labor forms does not verify that the
                                                      required annual work was not done. I f the
is to induce development of minerals and to
                                                       original locator can prove that the necessary
avoid speculative holding of claims. Casual
                                                      assessment work was done, he retains rights of
prospecting or surface sampling for the purpose
                                                      possession under Federal law.
of making a discovery will not serve as assess-
                                                          To the prospector or independent geologist,
ment work.
                                                      traveling to numerous claim groups and
   Over the years the courts have generally
                                                      performing assessment work can be an
prescribed rules governing the character o f t he
                                                      onerous and expensive task. Most mining
work and improvements that will satisfy the
                                                      companies with large claim holdings maintain
assessment work requirement. The court
                                                      a system of records in the company files and
rulings have been lengthy and complex, but
                                                      assign one man for part or all of the year to
they can be summarized as follows: the labor
                                                      keep track of assessment work and see that it is
and improvements, within the meaning of the
                                                      properly recorded. The Government may
statute, should be deemed to be done when the
labor is performed or improvements made for           under certain circumstances invalidate a claim
the purpose of working, prospecting, or               where assessment work has not been
developing the mining ground embraced in the          performed.
location, or for the purpose of facilitating the          Effective August 10, 1993, legislation was
extraction or removal of ore.                         enacted that affected the requirements of
   Claims may be grouped for assessment work          recordation of new mining claim locations or
purposes. That is, work can be done on one or         sites and annual assessment requirements.
more claims rather than on each claim in a            The new requirements can be found in 43
group, and the assessment work requirements           CFR Part 3830 - Location of mining claims.
can be met if the value of the work is sufficient.    The reader is advised to contact the local
The claims must be contiguous, that is, overlap       Bureau of Land Management office for fur-
or share common sidelines, and there must be          ther information.
  State law requirements are still to be fol-         Sometimes the mining company's counsel will
lowed. The claimant should consult with the           mistakenly advise a payoff; each time this is
State for these requirements.                         done it only compounds future difficulties.
                                                        There mav be circumstances where a group
                                                      of claims will appear to be abandoned. A search
    Adverse Proceedings                               of the county records fails to reveal an
   The problems of adverse claimants can fall         assessment affidavit for the immediate past
under two general categories:                         assessment year ending at noon on September
    1. A contest between two private citizens or      1. Inspection of the ground reveals no recent
companies over ownership of mining claims.            physical work of the kind required for
    2. A legal action initiated by the U.S.           assessment. Under these circumstances, a
Government against a mining claim held by a           new set of claims may be staked on what
private citizen or corporate claimant.                appears to be open ground. The new claimant
    In past years there was much litigation over      does the required location work and begins
extralateral rights, where avein apexed (fig. 2)      exploration--pursuit of discovery--on the
on one claim and extended down-dip off the            claim group.
claim. This type of litigation was commonly              If the former claimant has in fact abandoned
bitter and costly to settle. Extralateral rights      the claims there will be no problems; however,
litigation between two adverse claimants is now       if the former claimant had no intention of
uncommon, as negotiated settlements are               abandoning the ground there may be a legal
more satisfactory than drawnout expensive             contest over who has the best claim to the
lawsuits.                                             ground. If the original claimant has filed his
    Occasionally, two exploration groups may          proof of labor, the new claimant would have to
decide at approximately the same time to stake        prove that the assessment work had not been
a large block of claims over a target area where      done. Not having filed the proof of labor, the
exploration will be required to make a                original claimant now may be in the position of
discovery. One group may begin staking                 having to prove that he performed the required
claims first and the second group may stake           assessment work.
from the other end of the area, possibly not             Claims staked for leasable or salable
knowing of the competitor's activity, and a           minerals are subject to adverse action by the
"staking rush" is on when either or both of the       U.S. Government. The claimant is in trespass
parties discover the other's activities.              and may end up paying for the minerals that
    As they become aware of each other's              have been illegally removed. It is possible to
activities, the doctrine of pedis possessio (see      locate legal mineral claims covering the same
Protection Prior to Discovery section) will           ground where the U.S. Government has leased
come into use. One group may attempt to deny          or sold the nonlocatable minerals. No title is
peaceful intrusion onto its claims by the other       obtained to the nonlocatable minerals and
group. An adverse claimant situation often            their production cannot be impeded by the
exists between the two groups. The key to the         locator.
situation now depends on who can make a
discovery first, usually by drilling. Many              Many cases of unauthorized occupancy
complex legal problems may develop as the             have caused the Government to initiate an
claimants race to be the first to make a              action to remove a home or cabin or to correct
discovery.                                            some other nonmineral use.
    About this time, it is possible that a group of     Some claimants locate claims on land that is
floating older claims in the district will be         not open for mineral entry. This is often done
moved under the claims covering the new               where the locator believes the claims to be in a
discovery area. There is also the possibility         different section of land than they actually are.
that placer claims w i l l be staked b y              This may be a surveying problem, or the
unscrupulous individuals over the discovery           claimant may have failed to make the
area in the hope that the major mining                necessary check of the land management
company will buy out the nuisance value of the        agency records to determine the status of the
placer claims rather than fight in court.             land.
    Congress has given the Department of the           against an adverse claimant under the doctrine
 Interior adjudicative powers in matters relating     of pedis possessio by actively pursuing
 to the mining laws. The most common action is        discovery and maintaining continuous
 a contest of claim validity conducted under the      exclusive occupancy. This doctrine provides
 regulations of the U.S. Department of Interior.      only tenous prediscovery protection and it is
 The Department of the Interior's authority in         not possible to generalize as to what action will
 this area has been confirmed by the U.S.             satisfy the requirements in all cases; litigation
 Supreme Court. The administering agency               my often result.
 can initiate a complaint which will result in a         The claim locator has the right to prospect,
 contest through the Department of Interior           develop the mineral potential, do assessment
 under the Administrative Procedures Act for a       work, and perform other acts related to ex-
variety of reasons, including lack of discovery.     ploration that are not forbidden by law or
Necessary a c t i o n may be i n i t i a t e d       regulation.
simultaneously in the Federal Courts to resolve          Where there are conflicting or overlapping
urgent conflicts. After proceeding through the       claims, most rights are determined on the basis
Department o f the Interior regulations              of priority of discovery, but subsurface rights
process, the contest may go to the U.S. District     are not necessarily so determined. Extralateral
Court with appeals to the Circuit Court or            rights to a vein are based on apex considerations.
Supreme Court. Where the contest is of great             Valid, unpatented mining claims are real
magnitude, considerable time, money, and             property in the full sense of the term, except as
effort can be expended in actions of this type.      modified by multiple use legislation. When all
   At the time of application for patent, there is   requirements have been met, the locator has a
a GO-day period when adverse claims can be           valid, marketable title for mining purposes. As
filed with the office where the patent               long as the locator complies with Federal and
application was initiated. An adverse claim          local laws and regulations in good faith, he has
may be brought by another claimant who can           possessory title segregated from the public
demonstrate a right to all or a portion of the       lands, although the paramount title remains in
claim being patented. There is also an               the U.S. Government until a patent is granted.
opportunity for persons in the vicinity of a         This possessory title may be maintained
mining claim to protest that the patent              indefinitely as long as the appropriate laws are
applicant has not met the mining law                 complied with. This title does not include
requirements. Protests against a patent can be       timber except as used for mining purposes on
filed by the Forest Service at any time before       the claim, nor the right to nonmining useof the
patent for noncompliance with discovery or           surface. Assessment work must be done on the
labor requirements.                                  claim in the amount of $100 per claim for each
                                                     assessment year to maintain the possessory
                                                     title. The assessment year begins at noon on
     Rights of Claimants                             September 1 of each year.
  Under the United States Mining Law of 1872,            A claim locator who does not perform
the locator of a valid mining claim that has          assessment work for a period may resume
been perfected by the discovery of a presently        such work at any time, in the absence of the
marketable mineral deposit and by the                 intervening rights of an adverse claimant on
performance of all the required acts of location      the ground. The original claim locator regains
acquires the exclusive right of possession and       the same rights and title he obtained by
enjoyment of all of the locatable minerals            locating the original claim, providing that he
within the boundaries of his location. He also       can demonstrate the existence of a valuable
acquires any appropriate extralateral rights         deposit of a locatable mineral.
along with the use of the surface compatible             The U.S. Government may initiate a contest
with the Multiple Surface Use Act of 1955.           using the Bureau of Land Management
  Prior to the discovery of a presently              adverse claim procedures for cause affecting
marketable mineral deposit within the claims         the legality of a mining claim. The procedure is
boundary, the claimant has a questionable title      set forth in the Federal statutes as supple-
to the claim. Prediscovery rights can be held        mented by Department regulations.
     In a mineral contest between the Govern-         surface of mining claims. Under the Act any
  ment and a claimant the Government is requir-       mining claim located after July 23, 1955, shall
 ed to present prima facie evidence (evidence         not be used prior to the issuance of patent for
 sufficient to raise a presumption of fact or         any purposes other than prospecting, mining,
 establish the fact in question unless rebutted)      or processing operations and uses reasonably
 that the claim is invalid. The claimant has the      incident thereto. The rights of the holder of a
  right to retain expert assistance in defending      claim staked after July 23, 1955, and prior to
  his position and must show by a preponder-          patent are subject to the right of the United
 ance of evidence that his claim is valid.            States to manage and disposeof thevegetative
     In actual practice, the average claimant has    surface resources and to         manage other
 not made a valid discovery prior to locating his    surface resources, except the locatable
 claim. Many claimants mistakenly believe that       mineral deposits on the claim.
 compliance with State location laws ful-               The Act also provides that mining claims will
 fills the Federal requirement of discovery. It      be, prior to issuance of a patent, subject to the
 is common for a claimant to refer to having         right of the Government to use so much of the
 done the discovery work on a claim when in          surface as may be necessary for access to
 actual fact he has done the State-required          adjacent land. Any use of the surface of the
 location work.                                      mining claim by the Government must not
     Under the Multiple Surface Use Act of July      endanger or materially interfere with prospect-
 23, 1955, prior to the issuance of a patent the     ing, mining, or processing operations or uses
 United States and its licensees have the right to   reasonably incident thereto.
 use as much of the surface and surface                 The holder of a valid mining claim is still
 resources as is necessary for access to             authorized to cut and use timber from the claim
 adjacent land, providing that this use does not     for mining purposes.
 interfere with prospecting, mining, or pro-            The result of this legislation is that the
cessing. The claimant does not have the right        owner of a mining claim is entitled to use the
to use an unpatented mining claim for pur-           surface only as necessary for the mining
poses other than prospecting, mining, or             operation, and the claims are subject to sur-
processing operations ana uses reasonably            face managment by the Federal Govern-
incident thereto. In the interpretation of what      ment until patented.
is "reasonably incident thereto," there are gray
areas subject to various interpretations.
    The claimant has the optional right to apply
                                                                  occu          ncy
for a patent. The conditions that must be met          The mining laws permit a claimant to make
prior to filing an application are: a valid          reasonable use of the claim surface area prior
discovery of a valuable mineral deposit, the         to a patent being granted, so long as this use is
performance of $500 worth of improve-                connected with mining. The mining laws do
ments which directly facilitate the develop-         not permit the use of an unpatented mining
ment of the mineral deposit, and the prepara-        claim for land on which to build a home or
tion of survey plat and field notes by a             cabin. There have been many cases where
Deputy U.S. Mineral Surveyor. If the patent          persons unfamiliar with the mining laws have
application is successful, the claimant must         built homes or cabins on claims staked with
pay for the land at the rate of $5 per acre for      this idea in mind, or purchased as cabin sites.
a lode claim and $2.50 per acre for a placer            The Mining Claims Occupancy Act passed
claim. After patent, the surface and minerals        by Congress in October 1962 enabled people
on the claim are private land subject to local       making their principal residence on an im-
property taxation, and the annual assessment         proved site on a mining claim to occupy the
work is no longer required.                          land which the residence occupied. The law
                                                     was extended until June 30, 1971.
                                                        Buildings necessary for mining facilities are
    Multiple Surface Use                             allowed on valid mining claims when discovery
        Act of 1955                                  is not an issue. It is often necessary to erect
                                                     buildings on unpatented mining claims to
  Congress enacted the Multiple Surface Use          protect equipment, store samples, or house
Act in 1955 to curtail nonmining use of the          personnel.
   In dealing with unauthorized occupancy           quite literally the statement in the United
there is commonly a question of what is              States Mining Law of 1872 that the locator
authorized use for mining purposes. Even if the      acquired the exclusive right of possession and
 claim is valid, the occupancy may exceed that       enjoyment of all the surface included within
needed for mining purposes. Some habitation         the lines of his location. Miners commonly
of buildings can very well be an authorized use.     clear timber on a claim for development pur-
The administering agency should obtain a             poses, used it in surface structures and in
technical opinion regarding the claim validity       underground workings, and sometimes sold
before questioning possible unauthorized            the timber outright. Prior to 1955, the miner
occupancy.                                           had no right to sell the timber except for clear-
                                                     ance, nor could the Government remove or sell
                                                    the timber on a claim except in the case of an
     Trespass Limitations                           emergency or insect infestation. In 1955,
   The owner of an unpatented mining claim          Congress enacted the Multiple Surface Use
 has only limited rights to prevent trespass. He    Act to curtail nonmining use of the surface of
 does not necessarily have the right to fence the    mining claims. While the locator's possession
 claim and erect no trespass notices. Under the      and enjoyment is exclusive for mining pur-
 Multiple Surface Use Act, the surface may be        poses, the Government and its licensees may,
 used for nonmining purposes such as hunting         under proper circumstances, exercise rights of
 and fishing by persons other than the claim        way across the claim so long as in so doing
 holder.                                            they do not interfere with the mineral develop-
   After a valid discovery of valuable mineral       ment of the claim.
 has been made, the claimed area is no longer          On an inactive mining claim no trespass is
unappropriated public land. The intent of the       committed by people passing through the area
 law is that the same ground cannot be located      hiking, hunting, rock collecting, fishing, or for
or possessed by another claimant until such         numerous other reasons. Prospectors and
time as the claim is abandoned by the original      geologists may examine the showing on a
claimant.                                           claim without prior knowledge of its status as a
   Active mining operations obviously have a        mining claim or what the ownership is. It is
right to forbid trespass in and around              common practice t o examine mineral
buildings, mine workings, and mills. For this       showings and quickly map and sample the
purpose, fences and no trespassing signs are        surface and underground geology of a prospect
commonly erected.                                   without contacting the owner of a claim. If a
   Trespass on mining claims may be an              prospector or geologist spent the time nec-
accident or innocent mistake, intentional and       essary to contact all absentee owners prior to
justifiable, or intentional and not justifiable,    examining all prospects more time would be
and may be committed on the surface or              spent trying to find people than in looking for
underground. A person entering within the           ore. This type of examination is often to the
sidelines of another miner's lode claim for the     advantage of the absentee claim owner, for if
purpose of mining is a trespasser if the vein       something of interest is found in the
being mined apexes (see fig. 2) on the miner's      examination the owner will be contacted. I f
claim. The corner monuments of adjacent             nothing is found he is not bothered unneces-
claims may be placed on the surface of ad-          sarily.
jacent unpatented or patented mining property          I f the owner of a valid mining claim is work-
for the purposes of squaring the located claim.     ing the claim it is the usual custom for the
The consent of the owner is not essential when      prospector or geologist to stop and talk, and to
the encroachment is open and peacefully done.       gain permission to look around.
The right of the overlapping locator is limited        There is an occasional hermit or reclusewho
to the ground outside of the prior located claim    does not want anyone to come near his work-
or patented ground, except for extralateral         ings, let alone examine the geology or sample
rights that might be acquired. Subsequent           the showings. Unless the showings are of un-
objection by the prior owner is unavailing.         usual merit the prospect will go undeveloped
   Prior to the Multiple Surface Use Mining Act     while such an individual is in possession of the
of July 23, 1955, claimants commonly took           claims.
 Federal and State Safety                          apply (Mineral Resources o n National
                                                   Forests Use Under U.S. Mining Laws, Title
      Requirements                                 36, Code of Federal Regulations, Part 228).
                                                      All mine development programs on public
   The conditions of safety around a develop-
                                                   land must comply with appropriate regula-
ing or operating mine are controlled by both
                                                   tions.
Federal and State laws. The mining States have
                                                      At the earliest possible time, the manager of
State mine inspection organizations that in-
                                                   an exploration project with the potential for
spect and advise on the physical condition of      developing into a producing mine should be-
an operation.                                      gin keeping an environmental analysis record
   On the Federal level, two safety inspection     of the condition of the air and the water in any
organizations exist. These are Mine Safety         stream or lakes on or near the project, the con-
and Health Administration (MSHA), an agen-         dition of trees and vegetation, and any wildlife
cy of the U.S. Department of Labor, and Oc-        disturbance resulting from the project. This
cupational Safety and Health Administration        environmental baseline data may prove es-
(OSHA), also an agency of the U.S. Depart-         sential in demonstrating what environmental
ment of Labor. These agencies have pre-            changes occur, if any, as the result of the min-
pared pamphlets explaining their functions.        ing operation.
   The activities of MSHA and some State              Environmental analysis and the preparation
mine inspection organizations overlap and          of the required statements, plans, reports, and
some coordination exists where the State           following correct, established procedures is a
group has agreed t o Federal standards. All        complicated task which usually should be
three groups keep records and investigate          done by experts. In most cases, a mining com-
serious accidents and fatalities at mine           pany bringing a new mine into production em-
operations.                                        ploys full-time personal or consultants to do a
  The Bureau of Mines has a safety demon-          complete job of environmental analysis. In the
stration group, operating out of Boulder City,     case of the small operator, where the project
Nevada, which researches and devises safer         will not financially support expert help, the
methods for performing various tasks.              best plan is to obtain the necessary informa-
  Most western States have laws requiring that     tion from the proper authorities prior to pre-
shafts, drill holes, tunnels, and small pits be    paring a statement for submittal.
covered or fenced where they can be a danger          The Mining and Minerals Policy Act of 1970
to life.                                           declares that it is the continuing policy of the
                                                   Federal Government in the national interest to
                                                   foster and encourage private enterprise in the
          Environmental                            development of an economically sound and
                                                   stable domestic mining industry, the orderly
           Regulations                             and economic development of domestic re-
  The National Environmental Policy Act of         sources and reserves, and the reclamation of
1969. as interpreted by the courts and imple-      metals and minerals to help assure the fulfill-
mented in the regulations of the various in-       ment of industrial, environmental, and security
volved agencies, has added an important dimen-     needs.
sion to the preparation of plans for exploration
and development of resources on the public
lands.
  An Environmental Impact Statement is not                   Forest Service
required for every transaction involving re-
source development. It is possible to prepare a
                                                              Regulations
negative declaration when, based on an impact         Forest Service Regulations, 36 CFR 228,
appraisal, no significant impact is anticipated.   provide for a minimum adverse environmen-
A nominal impact declaration is also possible.     tal impact on the National Forest System
Proper authorities must concur. If National        surface resources from mining operations.
Forest lands are involved, the new regulations
   To minimize surface resource impact on             be used, the period during which the proposed
mining claims, the regulations require that           activity will take place, and measures to be
an operator who is conducting prospecting,            taken to meet the requirements for environ-
exploration, development, mining, or pro-             mental protection.
cessing of mineral resources in a National               The plan of operations must cover the re-
Forest file a notice of intent or plan of opera-      quirements reasonably foreseen for the opera-
tions when the proposed work may cause a              tion for the full estimated period of activity.
significant disturbance of the surface                Whenever the operator proposes operations
resources.                                            not foreseen in the initial plan, he must file a
    The notice of intent is submitted to the          supplemental plan or plans.
 District Ranger for determination of significant        Approval must be obtained of a proposal to
disturbance of the surface resources. If signifi-     build an access road to the project area to be-
 cant disturbance will result, in the opinion of      gin any planned operations. Without reason-
the District Ranger, the operator is required to      able access, many exploration projects are not
submit a proposed plan of operations.                viable. Exploration activity in the National
    A notice of intent and a plan of operations       Forests can be delayed by requirements im-
need not be submitted for prospecting opera-         posed under the National Environmental
tions that use existing roads and occasionally        Policy Act.
remove samples in a manner that will not cause          After the Forest Service completes an envi-
significant surface disturbance. Claim staking       ronmental analysis in connection with each
subsurface operations, and work that does not        proposed operating plan, the Forest Service
disturb vegetation or use mechanical earth-          officer will determine whether an environ-
moving equipment are exempt from the notice          mental statement is required. Not every plan of
requirements under the regulations.                  operations, supplemental plan, or modification
    The notice of intent to operate must provide     will involve the preparation of an environ-
enough information to identify the area              mental statement. Environmental impacts will
involved, the nature of the proposed opera-          vary substantially depending on whether the
tions, the route of access, and the method of        nature of operations is prospecting, explor-
transport. The District Ranger must notify the       ation, development, or processing, and on the
operator within 15 days if a plan of operations      scope of operations (such as size of opera-
is required.                                         tions, construction required, length of opera-
   The notice of intent may be bypassed by           tions, and equipment required) resulting in
filing a plan of operations when the operator is     varying degrees of disturbance to vegetative
certain that his operations will cause a signifi-    resources, soil, water, air, or wildlife. The Forest
cant surface disturbance.                            Service will prepare any environmental state-
   The plan of operations must include:              ments that may be required.
    1. The name and legal mailing address of the        When the District Ranger receives the pro-
operator (and claimants if they are not the          posed plan of operations he must promptly
operators) and their lessees, assigns, or            acknowledge its receipt.
designees.                                              The authorized officer must make an envi-
   2. A map or sketch showing information            ronmental analysis within 30 days and:
sufficient to locate the proposed area of opera-        1. Notify the operator that he has approved
tions on the ground, existing and proposed           the plan of operations, or
roads or access routes to be used in connec-            2. Notify the operator that the proposed
tion with the operations as set forth in the regu-   operations are such as not to require an opera-
lations, and the approximate location and size       ting plan; or
of areas where surface resources will be                3. Notify the operator of any changes in, or
disturbed.                                           additions to, the plan of operations deemed
   3. Information sufficient to describe or iden-                             ui e
                                                                               o
                                                     necessary to meet the p r s       of the regula-
tify the type of operations proposed and how         tions; or
they would be conducted, the type and stand-            4. Notify the operator that the plan is being
ard of existing and proposed roads or access         reviewed, but that more time, not to exceed an
routes, the means of transportation used or to       additional 60 days, is necessary to complete
the review, setting forth the reasons why addi-       suggest reasonable means of correcting the
tional time is needed. Provided, however, that        problem. The Forest Service may attempt to
days during which the area of operations is          close down an operation that is causing ir-
inaccessible for inspection shall not be in-         reparable and unnecessary injury to the sur-
cluded when computing the 60-day period; or          face resources.
    5. Notify the operator that the plan cannot         The Forest Service will arrange for consulta-
be approved until a final environmental state-       tion with the Geological Survey and the Bureau
ment has been prepared and filed with the            of Mines or other appropriate U.S. Department
Council on Environmental Quality.                    of Interior agencies on significant technical
   New regulations dated November 4, 1993            questions of geology, development systems,
(36 CFR Part 215) supercede the time                 techniques, and equipment. The operator may
frames for approval of operating plans               request this type of consultation.
under 36 CFR 228 (A).                                   All of the information will be available for
    After an operation begins, the Forest Service    examination by the public, except for informa-
 has the right to inspect the operation and issue    tion and data designated as confidential by the
notices of noncompliance with the plan. Non-         operator. Confidential information might in-
compliance notices must indicate what is             clude trade secrets, privileged financial and
needed to correct the problems identified.           commericial information such as the known or
    Some considerations in environmental pro-        estimated outline of a mineral deposit and its
tection are: air, water, solid wastes, scenic        exact location, the details of an exploration
values. fish and wildlife habitat. roads, reclama-   project, and other competitive commercial
 tion, erosion, landslides, water runoff, control    information.
of toxic materials, reshaping and revegetation          An operator aggrieved by a decision of an
of disturbed areas, and rehabilitation of fish       authorized officer may file an administrative
and wildlife habitat when the operation is           appeal through the Forest Service appeal sys-
completed.                                           tem set out in the regulations. Appeals beyond
    After the operation ceases permanently, the      the prescribed system should go through the
site must be cleaned up within a reasonable          appropriate courts.
time. This may include removing equipment               The regulations are applicable in Wilderness
and structures or other facilities.                  and Primitive Areas as long as the mining laws
    When a plan of operations is filed, a bond       apply in these areas.
may be required assuring that reclamation is            These regulations are a part of a vigorous
completed in accordance with the plan of             program to minimize surface damage from
operations.                                          mining in the National Forests. Care will be
   While awaiting approval of the plan of opera-     taken that the regulations are not unreason-
tions the authorized officer will approve the        ably used to restrict the statutory right that the
w o r k needed t o p e r f o r m assessment          miner has to prospect for, and develop, min-
requirements.                                        erals in public lands open to entry.
    During operations under an approved plan,           The regulations are in Title 36, Code of
the authorized officer may request a modifica-       Federal Regulations. A question and answer
tion to minimize unforeseen significant disturb-     pamphlet on this subject has been prepared by
ances. The Forest Service may be required to         the Forest Service.
                                                               PROSPECTING                          I


   The role of the small prospector-miner has        prospector must possess considerable geo-
been somewhat distorted by romanticists, who         logic knowledge and insight. It does not follow,
gloss over the complex series of steps neces-        however, that the prospector must be a geolo-
sary to take a prospect into production.             gist. Many geologists are poor prospectors.
Perhaps only in the early gold placers of            They are trained to move relatively rapidly
California, Idaho, and Montana were                  across the ground, recording and interpreting
conditions favorable for the individual miner of     a variety of information, often of little direct
early years to develop a small profitmaking          significance to ore potential but necessary for
operation while keeping himself fed and              complete reports and maps.
clothed, using no resources other than his own          Most professional geologists are salaried
sound health and optimism. From time to time,        employees or contractors and are reimbursed
other commodities are mentioned as the hope          for field expenses. Few prospectors are sup-
or refuge of the small miner, such as tungsten,      ported, if at all, beyond a minimum subsistence
uranium, and quicksilver, but over the long run,     level. The typical prospector depends largely
most metal production comes from large effi-         or entirely upon the development of his mineral
cient operations r e q u i r i n g huge capital      discovery for financial reward, recognition,
investment.                                          and his own personal sense of achievement. A
   In the rare instance where a prospector is        small number of professional geologists work
successful in finding a promising mineral            independently in mineral exploration, obtain-
showing, his first thought is almost always to       ing financial support from small companies or
sell out to someone more interested than he in       investors' syndicates.
developing a mine. Much of his off-season ac-           Corporate geologists involved in the search
tivity is in the submittal of his prospects to es-   for minerals most often work as a part of ateam
tablis hed companies. The prospector does not        of professional specialists, technicians, con-
consider himself to be a miner, although he          tractors, and consultants. The exact makeup of
often seeks temporary employment at an oper-         this group varies from one area to another, and
ating mine in order to replenish supplies, pay       depends to a great extent upon the particular
bills, or to wait out the winter season.             concepts and techniques employed.
   There is obvious romantic appeal and adven-         Typically, in addition to the geologist,such
ture in prospecting, and the possible financial      diverse talents are represented as those of the
reward would seemingly be an irresistible in-        geochemist, geophysicist, mining engineer,
centive. Great personal satisfaction can be de-      metallurgist, attorney, mineral economist,
rived from watching one's preliminary ideaof a       photointerpreter, computer expert, laboratory
prospect develop into an important resource.         scientist (such as a mineralogist), and field
However, few people seem able to become              technician. Any of these company personnel
proficient at prospecting or to stay at it long      might refer to himself or be called an explor-
enough to be reasonably confident of success.        ationist. Although the exploration work that he
   Considering the nature of ore deposits, min-      performs might sometimes be described as
erals, and the enclosing wall rocks, it is obvious   prospecting, he does not think of himself as a
that the fundamental basis for all prospecting       prospector, nor is it likely that anyone else
is the science of geology. To be effective, the      would refer to him in this manner.
    Usually the corporate explorationist's ac-       basis. A proficient prospector will have trained
tivities are called mineral exploration, orre-       himself well enough to be able to conduct in-
 gional mineral exploration where there might        dependent investigations into geological rela-
 be risk of confusion with physical exploration--    tionships he knows to be, or has been told are,
the systematic probing of a specific prospect        important in ore localization.
 by trenching, drilling, or underground work.            The greatest opportunity for the modern
   Prospecting is therefore usually the work of      prospector is i n following the development of
the prospector or the independent geologist,         new concepts of ore localization and new tech-
and includes ground reconnaissance and pre-          niques and instrumentation, which will allow
 liminary aerial observations. Only in special       him to confidently go back into areas inten-
situations is systematic physical work such as       sively prospected before by oldtimers. If the
sampling and drilling done at this stage. A cor-     prospector cannot find a new ore target or a
porate group usually refers to their preliminary     new approach, he depends far more upon a
mineral reconnaissance as mineral explor-           stroke of luck than prudence would justify.
ation. Exploration at the project level, such as        An easily read and comprehensive book on
drilling, trenching, and digging underground         prospecting has been published by the Cana-
openings, is called simply exploration, and         dian Department of Mines and Technical Sur-
considerable confusion can result when some-        veys ("Prospecting in Canada," by A. H. Lang,
one unfamiliar with the specific definitions        Third edition, 1970). This serious treatment of
used by an exploration group first comes in         the subject emphasizes Canadian conditions,
contact with them.                                   but most of it applies to prospecting anywhere.
   Prospectors can rarely afford to explore their    It is an excellent source of information for both
own prospects to any extent, and must interest       novice and professional.
a well financed, established mining organiza-           The modern prospector has advantages over
tion. In general, most prospecting or regional      the oldtimer in the form of better equipment,
mineral exploration is done before property         4-wheel drive surface vehicles, and aircraft.
acquisition is undertaken. Exploration is al-       Access into areas of interest is far better, and
most never started until property acquisition is    water, diet, and health conditions are not the
complete.                                           serious problems they were under more primi-
                                                    tive circumstances. Some mining experts
                                                    would counter with the observation that the
       The Conventional                             early prospector had to go in and stay in,
                                                    making him much more effective than some of
          Prospector                                the modern dilettantes.
   There are few people actively interested in          To become truly competent as a prospector,
prospecting today who do not havesome basic         a person should be prepared to devote at least
training in science or engineering, if nothing      as much time as he might to become skilled at
more than the typical requirements for gradua-      some other occupation such as automobile
tion from high school or an infantryman's map       mechanic or carpenter. He should read trade
reading course. Each year the opportunities         journals such as the "Engineering and Mining
expand for the average interested person to         Journal," newspapers such as the "Northern
study subjects such as basic geology and min-       Miner," and Government publications such as
eralogy. Short courses in prospecting or in         "Mineral Facts and Problems" by the Bureau of
specialized aspects of mineral exploration can      Mines and "United States Mineral Resources"
be attended by the private individual, although     by the Geological Survey. The latter volume
the location and timing of such offerings are       furnishes many important facts concerning
not always convenient.                              most mineral resources of interest, and con-
   Rather than describe today's conventional        tains many specific suggestions on prospec-
prospector as lacking in formal training, it        ting for various ore types.
would be more accurate to refer to him as a             To a lesser extent than in other vocations, it
person who has not been completely trained as       is possible for the beginner to seek out a sea-
a professional geologist and does not under-        soned professional prospector and to learn
take geologic work for others on a professional     from him directly. Such an apprenticeship
would obviously be of great value to the novice,    pressure f o r drastic restrictions o n all
but there is rarely an incentive for the exper-     prospecting and exploration activities. A great
ienced hand to share his knowledge and              deal of wisdom and fine judgment will be
experience.                                         required in finding ways to regulate the recrea-
   An experienced prospector who can effec-         tionist-prospector while not unduly restricing
tively communicate with people has little dif-      serious prospectors and geologists upon
ficulty today in obtaining company support or       whom the Nation depends for future mineral
the backing of a small investment syndicate         discoveries.
composed of local professional or business
people. The United States tax laws encourage
such individual investments, inasmuch as                    Regional Mineral
some exploration expenses can be written off
against other income. Long-term capital gain                  Exploration
schedules can be applied to some profits, and         When an established mineral organization
depletion allowances are an additional incen-       undertakes the exploration of a large new area,
tive to the investor.                               some considerations are simple and straight-
   For a variety of reasons, the number of full-    forward. Aside from the obvious desire to
time professional prospectors in western            continue i n the business of producing
North America has steadily dwindled, and             minerals, the organization may consider:
most of the important discoveries of recent            1. Need to diversify.
years, particularly in the United States, are the     2. Need to satisfy customer demand for a
direct result of mineral exploration done by         metal. Some manufacturers, after years of
corporations or by independent geologists.          dependence upon outside suppliers, may
                                                    decide to enter the mining field themselves.
                                                      3. State laws, local regulations, and
   Amateur Prospectors                              attitudes may encourage exploration in agiven
                                                    region.
   In recent years, as fu l I-time professional       4. The company may be well established in
prospectors have almost disappeared from the        some other profitable resource industry such
scene, amateur prospectors have become far          as petroleum, and be prohibited by antitrust
more numerous. To many outside of the               laws from purchasing o n g o i n g mineral-
mining business it is difficult to distinguish      producing companies. In such cases,entry into
between the two.                                    the mining business is said to be "via the
  The publicity, somtimes highly distorted,         exploration route."
given to rushes such as the uranium boom of           5. The desire to achieve or maintain a
              ~~
the 1 9 5 0 ' the convenience of modern off-road    reputation as the major supplier of a certain
vehicles,and the increasing amount of leisure       commodity, so that exploration leads of all
time available to so many, have combined to         kinds are investigated for this commodity,
produce tens of thousands of amateur                wherever they may be found.
prospectors. Some of these individuals make           As preliminary p l a n n i n g continues, a
great efforts to equip and train themselves, and    com bination of such considerations as these,
they are capable of finding prospects worthy of     guided to a large degree by the personal
exploration and development. However, the           judgment of a few individual decision makers,
majority of the amateurs are poorly motivated       will quickly focus attention upon certain areas,
and so lacking in the most rudimentary              often principally by a process of elimination.
knowledge that they create difficulties for         The resulting area of interest might be roughly
those seriously engaged in prospecting and          100,000 square miles in extent, something less
exploration.                                        than the area of one of the western States. It
  The amateur's common lack of                      may not be possible to further narrow down the
consideration for the rights of land owners, his    area of interest without at least a small amount
abuse of laws and regulations, and his ill-         of preliminary field reconnaissance.
conceived bulldozing of the surface have              In preliminary planning, a certain amount of
become so offensive that there is mounting          "elephant country" philosophy is involved in
selecting regions in which to hunt. That is, one    (fig. 3), where lime-silicate alteration formed
goes to Africa to hunt elephants. For example, in   around certain igneous intrusions in calcium-
planning the exploration for large low-grade        rich rocks such as limestone. The compilation
copper deposits, the obvious potential of the       for exploration of this ore type would
Arizona-New Mexico-Sonora region cannot be          emphasize the following geologic
matched elsewhere. Here,many great                  characteristics of the ore type; and the infor-
porphyry copper deposits are developed              mation would be gathered from literally
literally within sight of each other, and large     thousands of different published sources:
new deposits continue to be discovered in the          1. The location and character of igneous
region. There is probably no other area on          intrusives.
earth so intensively explored during the past          2. T h e d i s t r i b u t i o n o f c a l c i u m - r i c h
decade.                                             formations.
   Wyoming and northwestern New Mexico
                                                       3. P r e v i o u s l y d i s c o v e r e d s c h e e l i t e
have an impressive number of large, bedded          mineralization.
uranium deposits that can be mined by open            4. Showings of skarn.
pit methods, and general geologic conditions          5. Prospecting activity, particularly near
are permissive of many m o r e s u c h              known or suspected igneous intrusions.
occurrences. In north-central Nevada, a zone          6. Areas overlain by younger sedimentary
consisting of a dozen or so low-grade               and volcanic formations should be delineated
"invisible" gold deposits has recently been         carefully, for these rocks cover the
identified in which the important new Carlin        tungsten deposits.
deposit (the first major open pit gold mine in
North America) was recently discovered and is           Although this is a simplified description of
now being mined. Geologic conditions in the         the steps taken to evaluate a region for a simple
surrounding region suggest that similar             ore type, it illustrates the approach often used
additional deposits remain undiscovered and,        for whatever kind of ore sought. The emphasis
in terms of hunting for gold deposits of the        on different kinds of geologic evidence varies
Carlin type, this area is spoken of as "elephant    f r o m one ore t y p e t o another. The
country."                                           characteristic that may be important in
                                                    searching for one kind of ore may have little or
                                                    no significance in hunting for another. A more
   Exploration Concepts                             detailed discussion of the criteria for the
     Once an area of manageable size has been       recognition of various ore types is given in the
selected for regional mineral exploration, the      chapter titled "E~ploration.~'
first step is t o assemble all pertinent              A number of features of interest in regional
information such as published geologic maps         mineral exploration can be interpreted directly
and reports, private company data, commodity        on vertical aerial photographs, available from
maps, topographic map coverage, and aerial          the various Government mapping agencies or
photography. Some or all of these basic data        taken especially for the purpose.
are usually compiled on some suitable small-
scale map, such as the 1:250,000 U.S. Army            Most regional exploration leaves few marks
Map Service sheets published by t h e               upon the ground, and the work of the
Geological Survey. If the quality of published      prospector or geologist cannot be detected
geologic mapping permits, the basic geology,        after several storms wash away the imprint of
or skeletonized versions of it, is compiled. The    his boot. For every pit or other obvious sign of
objective of this work is to define those areas     fomer prospectors' interest, there are
which contain the right combination of              thousands of acres where the signs of
geological conditions to localize an ore            mineralization were t o o feeble t o have
deposit of the kind sought.                         attracted his attention. Much exploration today
   To illustrate the procedure, one of the ore      is done from aircraft or surface vehicles
types of interest in western North America          identical in every respect to other surface
today is tungsten (scheelite, C a W 0 4 )           users, and only the most experienced observer
mineralization found in distinctive skarn zones     is able to distinguish the explorationist's
              alluvium


              lava f l o w


              skarn tungsten
             (scheelite- CaW04)


              granite


              wall rock



                                  Figure 3.--Skarn tungsten mineralization.




activity from the comings and goings of other             concept i n presenting the project t o
scientists, resource managers, and outdoor                management.
enthusiasts.                                                 Often t h e preliminary report contains
  The corporate exploration geologist will                carefully prepared maps, quantitative data,
usually have received extensive indoctrination            photographs, and geologic cross sections. In
from his superiors concerning the various                 larger companies, where many different
rules to be observed on public land and the               exploration proposals may be considered
need for cooperation with agency                          simultaneously at regularly scheduled
representatives. He will be correspondingly               meetings, simplified diagrams are prepared to
receptive t o reasonable suggestions o r                  convey complex relationships and to serve as a
instructions, particularly where the law or               focal point for discussion and decisionmaking.
regulation clearly covers the situation in                   Each mining group or company has a
question.                                                 different objective in terms of size and type of
                                                          operation desired. The small mine that might
                                                          be financially successful for a small group or
Preliminary Evaluation of                                 individual is normally of no interest to a major
   Exploration Results                                    corporation. Mining ventures must be capable
                                                          of producing earnings of at least 5 to 10 cents
   Once specific areas of mineral potential have          per share if they are to be of interest to the
been defined, the results of prospecting or               typical mining company.
reconnaissance work are submitted t o                        Up to this point, the area being explored may
management before proceeding with property                have gone through a continuing process of
acquisition and physical exploration. Every               evaluation, however unsophisticated and
mineral exploration project requires                      incomplete. Analysis of cash flow is almost
preliminary estimation of the merit of starting           always done before the decision is made to
the work required to explore and develop the              proceed. These preliminary evaluations are
prospect.                                                 usually not identified as "feasibility studies,''
   The prospector or geologist makes an initial           although some of the same methods may be
rough estimate of the general form and                    used in deciding whether or not to continue. A
character of the expected ore body. The pros-             major feasibility study and t h o r o u g h
pector uses this original concept of ore in               evaluation is required to justify the multimillion
attempting to interest people in taking over or           dollar capital investment typical of a major
financing his prospect. The geologist uses his            mining operation.
I   EXPLORATION




   The selection of a small area for detailed         private land owners and prior claimants
exploration may be the result of regional             afterward, while completing the location
reconnaissance, a spot check of promising             requirements on the staked ground. A period
geologic situations described in published           of relative quiet usually follows this initial burst
literature, submittal of a proposal by a             of activity. Local residents may become
prospector or independent geologist, or the          somewhat frustrated at the apparent lack of
decision to restudy an old mine or mining            followup just when they have begun to be
district.                                            interested in developments. After sufficient
   The area selected for detailed work usually       ground has been acquired, detailed plans for
embraces additional ground outside the area          exploration are made, usually at a regional
of actual interest. This surrounding ground          office some distance removed from the
may not be concentric to the prime target area.      exploration project site.
A total of less than a square mile to as much as        The individual States specify the claim
10 square miles of land may be involved,             location requirements, and no two laws are
depending upon the type of mineralization            exactly alike. Most States, for example,
being explored. For example, the area required       Colorado and Nevada, have changed their laws
for a small high-grade mercury or gold               t o provide for staking claims without
prospect may consist of 10 to 100 acres, a           performing the physical "location work" which
massive sulphide base metal prospect a square        became so damaging t o t h e surface
mile or more, and major potash or phosphate          environment after the advent of the bulldozer.
potential might require acquisition of several       Some States require a map showing the
sauare miles of ~ r o ~ e r t v .                    location of the claim. This is done so that other
                                                     interested parties can find the claim on the
    Mineral rights are secured as soon as
                                                     ground, and to e l i m i ~ a t e the fraudulent
possible after the area has been determined to       practice of moving claims over discoveries
have exploration potential, although details of      made by others--the major abuse of the mining
property acquisition sometimes go on during          laws from the miner's point of view.
t h e planning and i n i t i a t i o n of physical
                                                        These new State laws eliminate poorly
exploration work. It is considered good              planned trenching and bulldozing at the time
practice to locate open ground before making         of claim location, but of course do not restrict
initial contact with the land owners and prior       or limit the carefully planned exploration work
claimants in the area. This sometimes leads to       the claimant may later do, nor minimize
misunderstandings, because ranchers often            assessment work requirements.
do not remember the relationship between
                                                        In many regions, indiscriminate bulldozer
their private land holdings and various surface      work i n performance of claim-staking
leases and informal agreements. They may
                                                     requirements is a far more widespread and
become upset over activity on what they have
                                                     serious disturbance of the surface than actual
come to consider their private property.
                                                     mining. Such senseless scraping of thesurface
  When undertaking property acquisition, it is       should be discouraged in those States where
necessary to move quickly, stake all open            the locator has theoption of not doing physical
ground, and undertake negotiations with              location work upon the ground.
                Planning                             tank trucks, and smaller vehicles used in
                                                     transporting men and equipment are heavy
  After mineral rights have been acquired and        duty, usually with 4-wheel drive, capable of
preliminary estimates of profitability made,         negotiating steep terrain over very poor trails
attention turns to the choice of exploration         and roads.
methods to be used and the sequence in which            When larger drills are employed, flat pads
they are t o be employed. Personnel                  as much as half an acre in size are leveled to
assignments are made, outside services               site the equipment, install mud tanks, and
contracted, and necessary equipment                  provide for sample collection and parking for
obtained and allocated.                              personnel. The smaller, skid-mounted drill
                                                     rigs can be moved under their own power by
                 Personnel                           utilizing the cable and draw works in a winch-
                                                     ing arrangement, to move them over bare
   A project manager is appointed, his title and     ground and up steep slopes to unprepared
 professional specialty depending upon the           sites. Auxiliary equipment such as pumps and
 kind of exploration work to be done. Most often     tanks can be pulled into position by the drill.
 he will be a geologist, and he will usually            Exploration drills and related machines are
 remain solely occupied with this project            powered by gasoline or diesel engines, and
through to completion.                               require a modest amount o i l ~ estorage at the
                                                                                          l
   All important contact should be with the          drill site. Electricity requirements are small,
project manager, for often he alone has the          and supplied by generators integral within the
 knowedge and authority to make decisions
                                                     equipment, or by small portable power plants
and to commit the company to a particular            of 1/2- to 5-kilowatt capacity.
course of action. Contractors' employees are
                                                        Trailer-mounted air compressors are used in
particularly to be avoided, for they may have an
                                                     some kinds of exploration drilling. Small track-
erroneous conception of the objectives of the
                                                     mounted, air-operated drills are available.
work, and are rarely authorized to talk with
                                                     These are maneuverable enough to work in
outsiders.
                                                     rough country without preparing elaborate
   Exploration projects such as d r i l l i n g
                                                     drill roads or constructing drill sites.
programs are commonly company training
                                                        If terrain conditions are unusually severe or
grounds for recent graduates and college
                                                     if road construction is impossible, helicopters
students on summer vacation. Such junior
                                                     can be used to mobilize and service the drills,
personnel usually have an imperfect
                                                     although at much higher cost. When not care-
understanding of the overall objectives of the
                                                     fully planned and efficiently utilized, helicopter
program. Unless it is made very clear that such      servicing of exploration drills becomes prohib-
employees can be contacted, unauthorized             itively expensive.
attempts t o obtain detailed i n f o r m a t i o n
                                                        Because of the large size of the drilling ma-
directly from them are almost certain to
                                                     chinery required on most modern exploration
jeopardize relationships with the project
                                                     projects, it is rarely feasible to use horses to
manager.
                                                     mobilize and service the work. The small port-
                                                     able drills advertised in rockhound news-
                   Access                            papers are not adequate for most exploration
   Provision must be made for acess t o the drill    work, and find application only in very special
sites, movement of staff and contractor per-         situations.
sonnel, water for drilling supplies, and removal
of samples. In the dry season, in highly fractur-
ed ground, exploration drilling may require                          Occupancy
thousands of gallons of water per day, and a            Where feasible, exploration work is based
major aspect of the work becomes the constant        from established motels, hunting and fishing
movement of large water trucks. Where water          camps, or ranches or farms. Families are usu-
is scarce, the drill contractor may purchase it      ally housed in mobile homes located in the
on some such basis as a flat fee per load paid to    nearest population center where utility hook-
the owner of a nearby well or pond. The drills,      ups are available. In more remote situations,
semipermanent or permanent buildings may              sible to locate the claims without doing bull-
be necessary, particularly after encouraging          dozer work or constructing roads, the surface
results are obtained from preliminary drilling.       disturbance being minimal, the job may have
The first requirement is usually for sample           been done without an operating plan.
handling in a geologic warehouse that can be            Construction or improvement of access
locked.                                               roads, drill sites, trenches, pits, or landing
                                                      areas for aircraft make it necessary to secure
                                                      an approved operating plan. The location and
            Communications                            nature of the work must be specified, and the
   Elaborate communications are usually not           work done in such a manner as to minimize
required on exploration projects except in the        surface damage and coordinate with other sur-
most remote situations. On large projects, or         face uses.
when work extends into the severe weather               The intent is not to regulate the mining in-
season, company or contractor may operate             dustry or to manage mineral resources, but to
radios to facilitate movement of men, equip-          minimize damage to the surface environment.
ment, and supplies, and to provide a measure          In some cases it will be necessary for the op-
of security in the event of sudden illness or ac-     erator to submit information normally regard-
cidental injury.                                      ed as secret or competitive within the mining
                                                      industry. In such cases, information necessary
        Property Adjustments                          for approval of the operating plan will be fur-
                                                      nished on a confidential, need-to-know basis,
   As attention focuses upon the specific target      preferably to a Forest Service mining engineer
area, it is sometimes necessary to make adjust-       or geologist.
ments in property or in the conditions of min-
eral ownership. For example, it may become
obvious that a certain area may be the only
suitable site for disposal of mill tailings, and
planning should begin to consider this as a rel-
                                                              Geological
atively inflexible fact.
   Before actual discovery of ore is made, a
                                                          Exploration Methods
minor overlapping of prior claimants' locations
might easily be resolved by asimple agreement            Understanding of the geology of the ore de-
to share royaltyon production that might come         posit and its general geologic setting is abso-
from the disputed area. It may be possible to         lutely necessary at every step in prospecting
secure agreement from all mineral claimants           exploration, and development. The principal
that vertical sidelines will determine mineral        method of portrayal of this information is
ownership rather than leave open the complex-         through the use of geologic maps and cross
ities of extralateral rights. Careful surveys of      sections, which are constantly reworked and
particularly troublesome claim boundaries             updated as work progresses and new infor-
may be contracted to a U.S. Mineral Surveyor          mation becomes available. Geologic maps and
with everyone's agreement to abide by his sur-        sections are fundamental in exploration plan-
vey. Reasonable discussion is usually possible        ning, correlation and evaluation of preliminary
before ore is found. After ore is found, the same     results, and in reporting to management.
suggestion might result in an immediate law-             The geologic field methods most commonly
suit or the threat of lease cancellation.             used are:
                                                         1. Geological detail is plotted directly on
                                                      field sheets made from maps published by the
 Contact With Federal Agencies                        U.S. Government, or made by Kelsh plotter
                                                      using large-scale aerial photographs taken
  In the earliest stages of planning physical ex-     especially for the purpose. Geology may be
ploration work, consideration must be given to        mapped directly on the aerial photographs
the operating plan to be submitted to the For-        from which the Kelsh map was made, or on en-
est Service if the claims are on National Forest      largements of them, and transferred to the
land. Up to this point, particularly if it was pos-   topographic base afterward.
                                                                          ,    E

   )
  1.           c l o s e d t r a v e r s e point

               supplemental          point


       o       detail point

           ,
   ;
  /'           underground workings
  /%




                                                                                   J       O        L
                                                                                                            100 feet
                                                                                                             A

                                   Figure 4.--Compass and tape method of mapping small prospects.



   2. Transit and stadia are used to prepare                            The geologic details shown on maps and
large-scale topographic maps and to record                           sections are observed in outcrops, excavations,
geologic detail simultaneously. The plane                            underground openings, and samples taken
table and alidade method, popular with Geo-                          from drill holes. The data obtained between
logical Survey and petroleum com pany geol-                          surface bedrock observations are plotted by
ogists, is little used in mineral exploration.                       careful projection and matching of known
  3. Brunton compass and simple optical                              data. Inspection of float (fragments of rock
rangefinders are sometimes used in detailed                          lying in the soil that are large enough t o be
mapping where extreme accuracy is not re-                            visually studied) is a method much used in pro-
quired. This method is popular with many geol-                       jecting geology.
ogists because it is possible to work alone.
   4. Brunton compass and tape (fig. 4) some-                           Criteria for Ore Recognition
times used to provide base control, make the
topographic map, and to record geologic de-                             The geologic features of importance in min-
tail where a large-scale map is required of a                        eral exploration vary considerably from one
small area. A closed Brunton compass and                             ore type to another, and what might be of im-
tape traverse is usually surveyed as the base                        portance in one ore type may be of minor signi-
control.                                                             ficance in another. However, there are a few
   5. Some geologists do preliminary geologic                        criteria for the recognition of ore that are al-
mapping of prospects on enlargements of ver-                         most always considered, regardless of ore
tical aerial photographs or small-scale topo-                        type, and a brief listing and discussion will
graphic maps available from various Govern-                          serve to illustrate the methods of the geologist
ment agencies. The initial saving in time and                        in exploration work. Some criteria for ore rec-
cost is more than offset by the frustration and                      ognition are:
slow pace of mapping this way. Serious errors                           1. Igneous rock affiliation.
of distortion result from enlargement to a scale                        2. Host rock association.
suitable for exploration work.                                          3. Wall rock alteration.
   4. Age of mineralization.                                and usually is subtle enough to have escaped
   5. Gangue mineral association.                           notice of the early prospectors and miners.
   6. Trace metal association.                                 Age of mineralization--Some ore deposits
   7. Structural controls.                                  occur only in rocks of a definite age. For ex-
   8. Physiographic expression.                             ample, much of the world's potash is Permian
   9. Weat hering effects.                                  in age (280 to 225 million years), and the bed-
   10. Ore mineralogy.                                      ded barite deposits of the West are largely re-
   Igneous rock affiliation--Many ore deposits              stricted to formations of Silurian and Devonian
are associated with or contained within certain             age (430 to 345 millions years). Many such
kinds of igneous rocks. For example, chromite               simple age relationships are only now becom-
ores are always found in a special kind of iron-            ing generally recognized, and the concept will
rich rock. Some types of tungsten mineraliza-               be helpful in the mineral evaluation of many
tion are always found associated with certain               regions.
granitic rocks.                                                Gangue m i n e r a l association--Many ore
   Host rock association--Certain kinds of wall             types have distinctive gangue mineral associa-
rock act as host to specific ore types. For ex-             tions (undesired minerals associated with the
ample, ancient reef deposits, similar to the mod-           ore) that can be of use in mineral exploration.
ern coral reefs of the South Pacific, are inter-            For example, two major regional ore belts, the
layered within marine formations such as lime-              Mother Lode gold and the Foothills base metal
stone. Fossil reefs are an important locus for a            zones of California come together and mingle
variety of important precious and base metal                northwest of Yosemite National Park. Prospec-
deposits.                                                   tors quickly learned that the appearance of
   Wall rock alteration--The mineralizing fluids            barite in float or in the prospect pan was good
that deposit ores sometimes permeate outward                evidence that the mineralization was of the
into the enclosing host rock, causing subtle                base metal type, not gold.
changes in a ring-shaped contact zone (aure-                   Trace metal associations--Many kinds of ore
ole) around the ore body (fig. 5). For example,             deposits have distinct combinations of minute
limestone surrounding certain silver-lead ores              amounts of metal found in association with the
is recrystallized to dolomite, coarsening the               principal ore metal, helping to distinguish one
texture of the rock slightly, and making it visi-           ore type from another. For example, the copper
bly lighter in color. The aureole of wall rock al-          deposit containing nickel and cobalt is of en-
teration is quite useful in mineral exploration,            tirely different character than a copper-
for it is much larger than the ore deposit itself,          molybdenum association.




                soi l


                ore


                al terat lon


                wall rock




                               Figure 5.--Wall rock alteration as a guide to ore.


                                                      30
                                  Figure 6.--Physiographic expression of ore.




   Structural controls--T he analysis of struc-           small specks of valuable mineral scattered
tural control of ore is usually of prime impor-          through a worthless rock matrix. The ore min-
tance in planning exploration, development,               erals themselves are often chemically unstable
and production. On a regional scale, ore de-              under the weathering conditions at and near
posits may be found in elongated rows of indi-           the surface. The ore minerals of copper, silver,
vidual ore occurrences or clusters of occur-              and uranium, for example, rarely survive in-
rences which are referred to as mineral belts or         tense weathering and are decomposed so that
mineral lineaments. Along these trends, above-           some or all of the metal is flushed from the out-
average potential for ore exists. On a more re-          crop in aqueous solution (ground water). This
stricted scale, the ore types of a given district         near-surface zone of leaching and flushing is
may occur along a single fault or beneath a              called the leached capping, and it may contain
thrust plane, focusing attention upon an unex-            none of the ore minerals characteristic of the
plored block of ground. Such relationships               unweathered ore deposit below. The recogni-
may become apparent only after the most pains-           tion of leached cap rock has been a very suc-
taking detailed geologic mapping.                        cessful tool of the modern exploration geolo-
   Physiographic expression--1 ndividu al ore             gist, because the various stable oxides, sul-
deposits, and sometimes entire mining dis-               phates, and carbonates of metals most often
tricts, are commonly altered, mineralized, and           remaining in outcrop are extremely difficult to
weathered so that the rock matrix consists es-           recognize and were easily missed by earlier
sentially of chemically unstable or soft, easily         explorers.
weathered minerals and rocks (fig. 6). Erosion              Ore mineralogy--1 n some instances the min-
cuts into such zones, and the resulting depres-          eralogy of the ore itself may be important. For
sions are often filled with gravel and lava flows        example, aluminum is one of the most abun-
and are usually densely overgrown with vege-             dant elements in the earth's crust, yet only
tation, all but concealing evidence of mineral-          bauxite (a relatively rare mixture of aluminum
ization. The recognition of mineralization               hydroxides) has been mined as an ore of
fringe effects, and the lateral projection of such       aluminum.
indications beneath cover, is an approach used              Most geologists have a checklist of ore cri-
by many explorationists.                                 teria they think important for each ore type of
   Weathering effects--Many of the mineral de-           interest. They might refer to the total picture of
posits currently of interest consist of relatively       all criteria considered together, as a "concep-
tual model" of that type of ore occurrence. They         Geobotanical methods of prospecting in-
may also have definite ideas about the size, shape,   volve the visual observation of changes in the
and grade to be expected of this hypothetical         normal appearance or distribution of certain
ore deposit. Obviously, a conceptual model            vegetation. The plant may show visible toxic
can be of great help in planning exploration,         effects such as deformed or discolored leaves,
during mapping and drilling, and in all phases        or unusual size. In some cases the very pres-
of the evaluation of results, if the risks inherent   ence o r absence of a given kind of vegetation
in any generalization are kept in mind. The use       may betray unusual nutritive or toxic condi-
of a formal conceptual model is often found to        tions. In one region, the discoloration of the
improve communications with management                leaves of a common tree, observed from fixed-
and to facilitate discussions between explora-        wing aircraft, led to the discovery of a major
tionists, such as those between geologist and         new copper district. In another area, the wide
geophysicist.                                         spacing of ashrub common to the region, with
                                                      intervening ground bare of grass, is a good in-
                                                      dication of the host rock of nickel silicate min-
                                                      eralizat ion.
       Geochemical                                       Various air "sniffing" devices are coming
                                                      into use in regional mineral exploration. Air-
    Exploration Methods                               borne, vehicle-mounted, and sample station
                                                      detectors have been designed to measure such
  The recent great progress made in rapid, in-        indicators as mercury vapor, sulfur dioxide,
expensive methods of trace metal analysis has         and radon gas in atmospheric and soil air,
resulted in a variety of applications in geology.     which may betray a weathering ore deposit be-
These are referred to as geochemistry. In min-        low the surface, perhaps even beneath a con-
eral exploration, geochemistry is broadly ap-         siderable thickness of soil.
plied in two different situations. Numerous              The geochemistry of surface and under-
samples are often collected incidental to other       ground water is a reconnaissance exploration
exploration work, such as geological mapping          tool. Samples from springs, wells, and streams
of underground workings. These samples are            may contain trace amounts of metal in solu-
submitted for trace metal analysis and the re-        tion, indicating that the water has come in con-
sults incorporated into the overall geologic in-      tact with a concentration of the metal, perhaps
terpretation. No confusion seems to result in         an ore deposit. Where surface water is insuf-
calling this work geochemistry, even though           ficient for adequate sample coverage, a popu-
the same term is used to describe trace metal         lar method is to analyze small samples of silt
analysis of air, water, soil, and rock materials      from the stream bed itself. This method enjoys
as an exploration method in its own right.            great popularity in more arid regions because
                                                      it is straightforward and can be done by tech-
                                                      nicians. However, results have proved very dif-
 Reconnaissance Geochemistry                          ficult to interpret and follow up, and much less
                                                      stream sediment sampling is being done today
   In applying geochemistry in regional mineral       than 10 years ago.
exploration, the basic requirement is for a
rapid, relatively inexpensive technique that will
efficiently narrow interest to areas small
                                                                         Rocks
enough to explore by more detailed methods.              Perhaps the most favored detailed geochem-
Simple observations can be made from the air,         ical exploration method at present is the col-
either visually, by the person in charge of the       lection of rock chip samples, analyzed to deter-
work, or by interpretation of aerial photog-          mine if significant patterns may guide explora-
raphy. Black and white and color photo-               tion. Many of the elements contained in ore de-
graphs are used, and false color effects are ob-      posits, and the surrounding envelope of al-
tained by using special films and filters to em-      tered rock, are not chemically stable in outcrop
phasize unusual rock, soil, and vegetative            and may be leached from the surface zone. For
effects.                                              example, a relatively high grade vein of copper
                                  Figure 7.--Metal zoning in a vein system.




may be so thoroughly weathered and flushed                Rock chip samples are transported from the
from the surface that no obvious copper min-              project area to a centralized company or inde-
erals can be visually identified, and geochem-            pendent laboratory for preparation and analysis.
ical values may be far below the metal content of
minable ore, although still high enough to be
indicative of commercial possibilities.                                       Soils
   Much rock chip geochemistry is done in the                In detailed exploration work, residual soils
hope that zonal patterns may be discerned,                are usually present, consisting of weathered
pointing to the area most likely to contain the           material derived from the underlying parent
ore deposit. A very simple pattern of progres-            bedrock (fig. 9). In many cases, analysis of
sive changes, upward and outward from the                 such soils reveals a pattern of enriched metal
central portions of the district may be envi-             values over the suboutcrop of the ore, when no
sioned. A typical zonal pattern for copper veins          visible float can be found at the surface. The
in the Rocky Mountains, as shown in figure 7,             method is far from infallible, and there are
may be quite different than for the zonation of           many variables that are either highly unpre-
a massive sulfide copper deposit, as shown in             dictable or imperfectly understood. Typically,
figure 8. Many variations of zoning are known             a few ounces of soil are collected at each sam-
for different kinds of ore, and are described in          ple site, rarely more than a few inches in depth.
the technical literature. Some companies have             The sample hole is usually filled in immediately
done original research and determined their               and the site marked by fixing a sample tag to a
own distribution patterns for ore types of inter-         nearby shrub.
est, often at great cost. Such privately devel-              A sample-site or campsite chemical analysis
oped concepts are closely guarded company                 is sometimes employed in soil work, using
secrets.                                                  either the entire sample or only the fine mater-
  Other than the stone bruises left by the col-           ial, sieved for analysis. Soil sampling does not
lector's hammer, rock chip sampling leaves no             leave signs of visible surface disturbance that
surface disturbance of a permanent character.             remain more than a season or two.
                                                                                      zinc

                                                                                      copper, z i n c

                                                                                      barium

                                                                                      copper, zinc, lead
                                                                                         (barium, c o b a l t , molybdenum)
                                                                                      copper

                                                                                      copper, c o b a l t , molybdenum

                                                                                      copper, molybdenum

                                                                                      molybdenum

                                                                                      massive s u l p h i d e copper ore




                                       -
                                                                                      wall rock


                                      0               2 0 0 feet



  1.   Zinc, copper                                                  IV.   Copper, z i n c , lead, c o b a l t , molybdenum
          (lead, barium)                                                     (barium, silver, arsenic)
11.    Z i n c , copper, lead, b a r i u m                           V.    Copper, c o b a l t , molybdenum
            (molybdenum, c o b a l t , s i l v e r , arsenic)                (zinc)
111.   Z i n c , copper, lead, b a r i u m , s i l v e r , arsenic   VI.   C o b a l t , molybdenum
            (molybdenum, cobalt)                                               (copper)


                            Figure 8.--Metal zoning i n a massive sulphide copper ore body.




        2000 -                                                                                 -
                                                                                                   metal content, of, soil
         1000   -                                                                              -   (parts per r n l~ ion)
                                                                                                                    l

             o O       "     -
                             p.




                                   Figure 9.--Geochemistry of residual soil over ore.
                 Vegetation                           magnetic behavior, electrical conductivity, and
                                                      radioactivity. Six basic geophysical explora-
  The biogeochemical method is used in de-            tion methods--gravity, seismic, magnetic,
tailed mineral exploration where the plant ma-        electromagnetic, electric, and radiometric--
terial is analyzed to determine trace metal con-      are commonly employed in the search for
tent. The plant may show no external evidence         minerals.
of abnormality. To be useful, the vegetation
must be fairly evenly distributed over the area
to be explored, and should be known to be a
                                                                        Gravity
reliable indicator on the basis of experience on         Gravity methods depend upon the relative
similar projects elsewhere or extensive experi-       density of the ore deposit and surrounding wall
mentation on the project at hand.                     rock, and are not much used in metalliferous
  The biogeochemical method has been used             exploration. Measurements can only be made
successfully where the needles of pinyon have         at fixed stations on the ground, and compli-
been found to contain unusual amounts of              cated corrections are required for station posi-
uranium over deposits of this metal. The pin-         tion and topographic conditions. The typical
yon, as in the case of a number of other trees        ore deposit is not dense enough, is too small
and shrubs, has the capacity t o selectively ab-      and irregular, and occurs in a deformed struc-
sorb an element through membranes in the              tural environment, making clearly defined
root system, and to concentrate the element in        gravity anomalies difficult to discern and in-
portions of the plant itself. The roots effectively   terpret.
act as a much larger sampling system than                The method has been very successful in ex-
single small handful of soil collected at thesur-     ploring for large deposits of petroleum, natural
face at one point.                                    gas, sulfur, and salt. Limited application has
  The principal objections to the biogeochem-         been reported in exploration for barite.
ical method are the difficulty in obtaining good
samples and the complicated sample proces-
sing and analytical techniques. The same part                           Seismic
of each plant must be collected if the results           Seismic methods have little use in metal-
are to be significant, and in some cases the          liferous exploration because of the relatively
sample must be collected at the same season           small size and complicated geology of the
of the year to yield consistent results.              typical ore deposit, and because of the high
  In recent years, biogeochemists have begun          cost of seismic work. The method depends
to use the mull (granular forest humus) found         upon the velocities of acoustical energy in
beneath trees. This partially decomposed              earth materials, and has been enormously suc-
material is easy to collect and analyze, and          cessful in searching for petroleum, natural gas,
contains a sufficient amount of trace metal to        and sulfur, where the large deposits may be lo-
be useful.                                            cated by simply determining attitude of the
  Using sampling techniques similar to those          enclosing strata.
used in botanical studies, biogeochemical
sampling leaves no permanent marks of
damage.                                                                Magnetic
                                                        Certain minerals distort the earth's field, and
                                                      where sufficiently large concentrations of such
        Geophysical                                   minerals occur, variations can be measured by
    Exploration Methods                               magnetometers mounted in aircraft, in ground
                                                      vehicles, or positioned at stations on the
   Some ore deposits contain minerals that            ground. Magnetite iron ores have been found
possess physical characteristics that can be          in many areas of the world using the airborne
measured by suitably sensitive instruments.           magnetometer.
Exploration based on the principles of physics          In one case in the western United States, a
is called geophysics. Exploration techniques          very large iron deposit has recently been dis-
utilize such physical properties as density,          covered beneath several hundred feet of barren
volcanic flow rock erupted over the ore de-               to exploration in the western United States,
posit. Magnetic copper skarn, magnetic nickel             where ore deposits generally have poor
ore, and asbestos-bearing serpentine asso-                electromagnetic response characteristics and
ciated with certain magnetic intrusive rocks              may be deeply and erratically weathered, fur-
have been found, using the magnetometer.                  ther destroying the ability of the ore to
Some geophysicists propose the use of the                 respond.
magnetometer to detect gold placer deposits,
because of their common association with                                     Electrical
black sands largely consisting of the mineral                Natural electrochemical reactions near the
magnetite.                                                surface of the earth, where metallic sulphides
                                                          may be subject to weathering, can be used in
           Electromagnetic                                the simple self-potential (SP) met hod. The
  Of the various electrical methods of pros-              measuring instrument detects the electrical
pecting, only the electromagnetic (EM) system             current developed during the weathering of the
can be used in aircraft. Airborne EM systems              sulphide, as shown in figure 10.
have been applied with great success, particu-               A shortcoming of the SP method is the fre-
larly in reconnaissance exploration for mas-              quency and variety of spurious responses ob-
sive sulphide ores on the Canadian Shield.                tained. A more popular application of the
   Electromagnetic methods energize t h e                 electrical method is where controlled electrical
ground inductively by means of an alternat-               energy is applied to the earth and the resulting
ing current flowing in a transmitter coil. The            electrical behavior of the ground is observed
resulting signal, containing ground response              at closely spaced stations at regular inter-
characteristics, is detected inductively by a             vals over the surface. An adaptation much used
receiver coil. Both coils may be mounted in the           during the past decade is induced polarization
aircraft, or both placed on the ground. In one             (IP) where the conductivity of mineralized
recently developed variation of the method,               ground changes with variation of frequency
the transmitting coil is on the ground and the            of the applied current, while the conductivity
receiver in the aircraft.                                 of barren ground remains constant. As with
  The method is relatively slow and expensive,            the SP method, IP often produces misleading
particularly when used on the ground in de-               results and use of the method has declined
tailed surveys. It has not been widely applied            recently.



          (Measurement of e l e c t r i c current spontaneously generated by a sulphide body)

                                                    ,measuring     instrument




                                    Figure 10.--The self-potential method.
                                                                                                     036



                                                                                                     025
 G    measurement stat ion
       (counts per minute)                                                                 than 2000 cpm


      supplementa l stat ion             035      072                                                034
        (verification of anomaly)

\     isorad contours                                                                                035



         0              200 feet


                                         (measurement of radiation by hand held geiger counter)


                       Figure 11.--Plan showing gamma radiation over a uranium ore body.




               Radiometric                                 in mineral exploration if properly coordinated
                                                           with basic geologic concepts and evaluated by
   Uranium, thorium, and potassium occur                   personnel experienced in ore search.
naturally in earth materials, and being radio-                Several applications of activation analysis
active, anomalous concentration may be                     techniques show considerable promise in
detected by radiometric surveys (fig 11). Only             mineral exploration, and improved versions of
gamma radiation is useful in exploration,                  instrumentation are becoming available for
because alpha and beta emissions are masked                field use. An intense radioactive source is
by a thin cover of soil, water, or air. Gamma ray          mounted within lead or paraffin shielding.
emissions penetrate only a few inches of soil              When the shielding is raised so that the surface
or a few hundred feet of air, so that the radio-           area to be sampled is subjected to radiation,
active ore deposit must virtually outcrop                  some elements respond be giving off a
at the surface to be detected.                             radiation that is measured by a counter within
  Geiger counters and scintillometers are                  the apparatus. The method might be compared
easily portable and can be held in the hand,               to an interrogation-reply mechanism.
mounted in surface vehicles, or operated from                 A typical portable instrument can be used
aircraft. Airborne radiometric surveys were                only for one element, and the equipment is
successful during the 1950's in exploration for            cumbersome, expensive, and must be
uranium in Colorado, Utah, Arizona, and New                operated by trained personnel under Energy
Mexico.                                                    Research and Development Agency (formerly
                                                           Atomic Energy Commission) license. In spite
             Remote Sensing                                of these shortcomings, limited use thus far has
  No ore deposit has yet been found directly               been spectacular in such applications as the
by the highly publicized "remote sensing"                  search for beryllium ores. Several major
techniques of exploration from spacecraft.                 deposits of beryllium have been found in old
Most of the methods used are adaptations of                mining districts generally considered to have
techniques well known and evaluated in a                   been thoroughly explored.
variety of laboratory, ground station, surface               Most ore deposits in the western United
vehicle, and aircraft installations. A tremen-             States do not respond well to any kind of geo-
dous amount of basic scientific data is being              physics or are too small and irregular to
collected which cannot fail to beof major value            produce an anomaly sufficiently distinctive to
interpret and explore. On the Canadian Shield,        expected to delineate ore, because these
the typical ores possess good geophysical re-         deposits contain no minerals capable of meas-
sponse characteristics. Outcrops were scoured         urably distorting magnetic patterns.
clean of weathering effects by Ice Age glacia-           It is obvious that the application of geo-
tion, so that weathering does not interfere.          physics involves more than the simple ability
The thin layer of glacial drift over much of the      to make the equipment work. To be success-
region made traditional prospecting methods           ful, the geophysicist must be thoroughly
ineffective, and many ore deposits have been          grounded in fundamental ore deposit theory,
discovered in recent years by geophysics.             or must work closely with an exploration
Canadian explorationists are therefore much           geologist in planning and interpreting the
more likely to be enthusiastic about geo-             work.
physical exploration than their colleagues in
western North America, who are more ac-
customed to the complicated, unresponsive,              Restudy of Old Mining
weathered ores of the deserts and mountains.
    The geophysical method that might be                      Districts
useful in one area may prove wholly inappro-             Only in very unusual cases is it possible to
priate in another. For example, airborne scintil-     reopen a mine and simply put it back into
lation counters were used very effectively in         profitable operation without doing additional
radiometric reconnaissance for bedded ura-            exploration or development. Previous mining
nium ores of the Colorado Plateau in Colorado,        may have been done in ignorance of a mineral
Utah, Arizona, and New Mexico. The same               that has more recently become of economic
technique, when applied to exploration for            interest, but in general, nothing of value was
uranium in Canada, was a total failure. It was        knowingly left by the oldtimers, or missed by
found that the Colorado deposits were relative-       scavengers during the first years after the
ly high grade, and enclosed in a sequence of          mine closed.
virtually nonradioactive sediments. The Cana-            Today, the exploration geologist reenters
dian exploration was conducted in a terrain           old mines and mining districts with an entirely
of granite and metamorphic wall rocks that            different point of view and approach. He
themselves were radioactive, resulting in such        researches old records and undertakes geo-
 a hash of background signal and false anoma-         logic work because the character of mineral-
 lies that the airborne surveys failed to delineate   ization may suggest the presence of an entirely
useful target areas within the static.                new ore type or because careful analysis of the
    In general, the most discouraging aspect of       geology of an old district might reveal new
geophysical exploration is the spurious result        possibilities at greater depths, along a faulted
frequently obtained. For example, the ore             trend, to one side of the old workings, or in
deposits that furnish t h e best electro-             some other unexplored situation nearby.
magnetic responses are massive sulphides,                In the study of old districts, great emphasis
which are found in rocks containing variable          is placed on geology and mineralogy, because
amounts of pyrite and graphite. The pyrite and        of the wealth of opportunities for inspection
graphite, which are worthless and commonly            and sampling provided by the underground
show no meaningful distribution pattern in            mine openings. Much can be learned from the
relation to the ores, yield a geophysical re-         study of structural control of the previously
sponse that cannot be distinguished from that         mined ores. Sometimes, relatively large
of the ore itself.                                    amounts of money are spent to reopen old
    Many exploration holes are drilled into elec-     workings with the immediate objective only to
tromagnetic anomalies, only to encounter bar-         do geologic mapping and sample the mine.
ren pyrite or graphite. Conversely, negative             Perhaps the most discouraging aspect of
geophysical results by no means rule out the          restudy of formerly productive areas is the
presence of an important ore deposit. For             effort and cost of land acquisition. Complica-
example, the most careful magnetic survey             ted mineral rights such as numerous small
over an "invisible" gold deposit of the kind          patented claims, fractions, lots, former town-
being found in northern Nevada could not be           sites, millsites, tunnel rights, and right-of-way
of various kinds make this work very expensive       and something might be blundered onto in the
and time consuming. The problem worsens              process.
with each new generation of heirs.                      Prospectors, and company geologists as
   Although the typical difficult property sit-      well, have been heard to remark that they pre-
uation is offset to some extent by the en-           fer to cut up the land visibly during the act of
thusiasm of working in an area where signs of        claim location, so that everyone will know the
mineralization abound, the project geologist         ground has been staked. Mining lawyers gave
must gather together enough hard geologic            this advice for years, prior t o the present con-
evidence to convince management to proceed           cern for the environment, and some still do.
with property acquisition before exploration           This kind of thinking has sharply diminished in
can begin. If the mineral rights to a sufficiently   recent years, especially where modern State
large block of ground in the typical old mining      mining legislation has made it possible to
district can be put together on reasonable           locate mining claims without doing physical
terms, even for a relatively short period of         work on the ground. These new attitudes have
time, management usually receives such pro-          already greatly reduced the amount of surface
jects with far more enthusiasm than pro-             disturbance over the past 5 to 10 years. In a
posals for exploration in virgin territory.          typical western State, tens of thousands of
                                                     mining claims have been staked annually. This
                                                     would have amounted to hundreds of acres
       Trenches, Pits,                               of surface disturbance under the old location
     Overburden Drilling                             requirements.
                                                        In serious exploration by trenching, bull-
   Preliminary exploration work may be under-        dozers of various sizes are used. Such equip-
taken by the conventional prospector, for            ment is easily available and usually is present
example, in trenching to establish the trend,        on the project for other work such as construc-
width, and mineral character of an oreshowing        tion of access roads or preparation of drill sites.
protruding from soil. Many types of ore              Mechanical or hydraulic rippers are used in
weather readily at the surface, and these            tough ground; drilling and blasting are rarely
surface effects must be removed if the true          resorted to because adequate samples can
character of the mineralization is to be             usually be collected at the point where the rock
determined. Preliminary trenching and pitting        becomes too hard to be moved by blade or
may be done with the idea of making the              ripper.
prospect interesting to the examining geologist         If additional depth is required in hard rock,
and to facilitate his work. Sometimes, the small     a shallow shaft is usually sunk at lower cost
miner or conventional prospector refers to           and with far less damage to the surface. Where
this as development, but this term is more           topography permits, the trenches are laid out
properly used in connection with the prepara-        at an angle to the contour so the bulldozer
tion of a mine for production after the presence     can more easily dispose of the spoil t o one
and general character of the ore deposit is          side. The face, or uphill side of the trench, is
proven.                                              used for geologic observation and sampling
   A large amount of the the surface disturb-        because it is clean of broken material, and sur-
ance on public land is caused when the ama-          vey stakes and sample tags are not knocked
teur prospector thinks he has located valuable       down easily by livestock and vehicles. It is
ground, and begins bulldozing while staking          normal practice to orient the trench at a high
claims. He enthusiastically scrapes into soil-       angle, as close to 90' as possible to the trend
covered areas of any kind with the idea that         of elongated bodies such as veins or mineral-
there ought to be a big mineral deposit in there     ized beds.
somewhere. The extreme futility is where such           Carefully planned trenching can contribute
poorly planned trenching is attempted in an          valuable exploration information, but much
area of 50 feet of soil cover. He may often          trenching is a complete waste of time and
decide to bulldoze crude trails on the ridge         effort, for example, in the fairly common sit-
lines while the bulldozer is on the property,        uation where the bulldozer operator himself
because in his mind this will improve access         plans the work for lack of good supervision.
   Backhoe trenching is becoming more popu-         on the bottom without risk of material falling.
lar in serious exploration work. Good trench        Pneumatic drills are usually used, and blasting
wall faces are cleanly and quickly exposed in a     is done with stick dynamite and standard fuse
variety of topographic and soil conditions,         and blasting caps. The broken material is
even on relatively flat terrain where the bull-     removed using buckets hoisted by hand
dozer would not perform well. It is possible to     windlass, small winch, or power takeoff units
cut backhose trenchesstraight down a hillside;      on tractors or trucks.
in fact, this is the preferred orientation of the      Overburden drilling is a specialized shallow
equipment for efficient excavation and dis-         exploration method used to obtain small
posal of spoil.                                     bedrock samples. The samples are used for
   Surface disturbance is less than with a bull-    geochemical analysis, in geophysical inter-
dozer, restoration of the surface is quite          pretations of various kinds, or for some in-
simple, and it is possible to selectively place     direct use, rather than as a prime exploration
the topsoil to one side and pile the deeper         method where ore itself is the object of the
material to the other side so that the trench can   drilling.
be refilled, reversing the excavation process
after geologic inspection and sampling of the
trenches. It is impossible to exactly restore            Exploration Drilling
the surface to original contour, because the           Exploration drilling is primarily aimed at
excavated material expands as much as 20            determining whether or not the ore target is
percent or more, resulting in overfilling of the    present, and if so, to obtain a preliminary idea
trench by this amount. Aside from reducing the      as to its size and grade. Secondary objectives
surface damage, it is considered good practice      may involve testing general geologic condi-
to backfill trenches to maintain good relations     tions, such as exact type of formation present,
with other surface users such as holders of         wall rock alteration, or geochemical zoning. In
grazing permits.                                    the ear-ly stages of the work, emphasis is
   Trenches were often excavated by hand in         placed on speed and cost, and if preliminary
exploration work prior to World War II. Rising      work is successful, a more accurate and more
labor costs and the general availability of         expensive drilling method may be used.
mechanized equipment make work of this kind            There are many drilling methods, but three--
too expensive to be cost effective today. Only      percussion, rotary, and diamond drill--are by
in extremely remote areas, service by aircraft      far the most common in exploration work. The
or pack string, is hand trenching considered        equipment may range in size and complexity
feasible. Standard hand tools such as long-         from simple, hand-operated augers to small-
handled shovels, railroad picks, pry bars, and      scale versions of the rigs used in oil field
brooms are used.                                    explorations.
   Shallow pits or exploration shafts are              The pattern and spacing of exploration drill
excavated where irregular deposits are              holes are dependent largely upon the size,
expected to extend beneath soil cover, or           geometric orientation, and internal distri-
where the alluvium itself is suspected to           bution of mineral values of the particular kind
contain valuable material such as placer gold.      of ore target involved. A clear conceptual
Soft, unconsolidate material can be dug with        model of the particular ore deposit of interest
small backhoes to depths of 10 to 15 feet, and      is of great help in laying out an efficient and
circular shafts several feet in diameter can be     economic drill hole pattern.
excavated with septic tank diggers to depths of        Most deposits large enough and homo-
about 100 feet. Only the uppermost weathered        genous enough to be mined by bulk methods
bedrock can be removed by these machines,           are drilled with vertical holes arranged in
and if penetration into the rock itself is          square, rectangular, triangular, or fence (row
required, standard methods of shafting by           of holes) patterns, as seen in plan view. Angle-
drilling and blasting must be employed.             hole drilling is necessary where steeply
   When shafting is undertaken, it is necessary     inclined vein deposits are being explored,
to securely timber the upper portions of the        and in general is more expensive than vertical
opening, so that men and equipment can work         drilling.
               Hand Drilling                         processing for analysis. Large percussion rigs,
                                                     such as those used in open pit copper mines
   Small, hand-operated drills such as the           for blast hole drilling, are too heavy and
augers and sample tubes employed in soil test        cumbersome to be used in exploration work.
work have limited application in mineral ex-         Churn drills, the cable tool rig formerly widely
ploration. Although heavy-duty versions of this      used for water well drilling, are no longer much
equipment have been manufactured and                 used in mineral exploration, except for small
equipped with lightweight, aluminum drill rod        specialized adaptations used in placer
extensions and tripod hoistworks, these drills       evaluations.
are useful only under near-ideal conditions,
and cannot penetrate bedrock. The most
common limitation is where hard boulders are                      Rotary Drilling
encountered in the soft soil matrix, or where
                                                        Rotary drills are relatively fast and
excessive moisture is found. The principal use
                                                     inexpensive to operate in a wide variety of
of hand drills is in testing abandoned mill
                                                     exploration conditions. Most of the rigs are
tailings, which are finely ground and even
                                                     truck-mounted and completely self-contained,
grained, and are compacted well enough that
                                                     including the air compressor. At higher
the hole will stay open without caving while
                                                     elevations, auxiliary compressors must be
samples are taken from progressively deeper
                                                     provided, because of the reduced compressor
depths.                                              efficiency. Standard tri-cone bits drill a hole 4
   Many different kinds of powered augers are        inches in diameter or larger, and drill cuttings
used in exploration, ranging in complexity           are blown out of the hole with compressed air.
from small, hand-held, post-hole diggers             A gasoline or diesel engine drives the unit.
powered by gasoline to the large augers used
                                                        Some of the equipment can be quickly
to set power poles. The most serious
                                                     converted for core sampling, although coring is
limitations are again boulders in the soil,
                                                     less satisfactory and generally slower than with
excessive moisture, and inability to penetrate
                                                     equipment specifically designed for t h e
far into the bedrock.
                                                     purpose. Most rotary drills are mounted on
                                                     trucks that require relatively good roads.
           Percussion Drilling                       Angle-hole drilling is not possible with most of
   Several of the compressed air drills used in      the rotary equipment available, and is a major
drilling and blasting have been applied to           limitation of the method.
exploration. The hand-held miner's drill,               Because rotary drilling is relatively rapid,
similar in size and appearance to a jackhammer,      samples were formerly piled on the ground in
is sometimes used in collecting small samples        rows, each pile representing from 2 to 10 feet of
in solid bedrock to a depth of about 10 feet.        advance, each row from 20 to 100 feet of hole.
Larger machines, such as the wagon drill used        In recent years, practice has been to place the
i n highway and dam c o n s t r u c t i o n , are    samples in containers and remove them from
mounted on wheels and can be towed to                the exploration site, partly t o leave a clean
difficult drillsites along with an air compressor    drillsite, but also to frustrate competitors'
mounted on a trailer.                                inspection of the drilling results and to permit
   Wagon drills, as well as a variety of small       geologic logging in more efficient conditions
track-mounted, self-propelled percussion             at the field office.
drills, can drill holes at any angle, often to          With equipment in good condition and a
depths of over 100 feet. The compressed air          skilled operator, progress of the typical rotary
that powers the drill is also used to cool the bit   rig will vary from several tens to several
and carry cuttings away from the face and out        hundreds of feet or more per 8-hour shift, and a
of the hole, where they are collected by simple      considerable amount of sample is generated,
sack holders, buckets, cyclones, or other            even using the smaller bits. Rotary drilling is
devices, depending u p o n the accuracy              particularly preferred in exploration where the
required of the sample. Percussion drill             sampling or logging is done "in-hole," as for
samples are usually placed in containers and         example where uranium is measured by
taken from the drillsite for logging and             scintillation probes run in and out of the hole.
  Some geologists object to rotary drilling                  Water is usually the drilling medium;
because the samples are broken into small                 compressed air, crankcase oil, or kerosene are
chips and fragments where the structure of the            used in special situations. The core sample is
bedrock cannot be seen. Others feel that the              cut by a circular bit embebbed or set with
relatively low cost and good progress of the              industrial diamonds. The core passes inside
method more than offset the disadvantage of               the circular bit face and is collected in a core
the sample obtained, and actually see some                barrel which retains the sample for removal
advantage t o t h e b r o k e n material f o r            from the hole. The material ground up by the
inspection and assaying.                                  diamond bit is called sludge, and is carried up
                                                          around the drill rod to the surface. The core is
                                                          placed in compartmented boxes and taken to
           Diamond Drilling                               the field office.
  Diamond drilling (fig. 12) is generally                    In some cases, the sludge is carefully
considered the most versatile drilling method,            collected and saved as an important part of the
providing a superior c o r e sample for                   drill sample. Sludge is collected in specially
observation and preliminary testing. The                  designed settling tanks and placed in metal
equipment can drill at any angle, including               cans for plastic containers for transport to the
upward from underground stations. Gasoline                field office for drying and processing. The
and diesel engines are most commonly used,                clear water is returned for drill use. Where the
although air and electric motors are available.           sludge is not saved, it is allowed to settle out in
Core recovery is not always good, particularly            the bottom of a rude pit called a mud sump,
in mineralized rock, and the method can be                which often overflows on hillside operations
painfully slow and expensive. Diamond drillers            leaving an unsightly smear of light-colored
are usually more experienced and may be                   drill cuttings down the slope. If drilling mud is
more highly paid than other drillers, for the             not carefully controlled while the work is in
work is more exacting.                                    progress, and if the mud sumps are not




                          Figure 12.--Diamonddrilling, collectionof sludge samples.


                                                     42
covered after t h e work is finished, a                 If deep penetration is desired, far below any
particularly unsightly and enduring blemish on       level for which mining may presently be
the surface can be created.                          planned, it is considered permissible to make
   A variety of additives are placed in diamond      one further reduction by setting "E" casing and
drill holes, mostly to eliminate lost circulation,   proceeding to the termination depth with EX
when the drill fluid is lost in fractures or         bit, thesmallest used in most American mineral
caverns and no sludge sample returns to the          exploration. EX bits cut a hole 1-1/2 inches in
surface. Various organic and inorganic               diameter and a core 7/8 inch in diameter. Such
materials such as beet pulp, horse manure, and       a sample is usually considered too small to be
bentonite have been used, along with a number        reliable in serious evaluation of large bulk
of specially prepared muds developed for use         mining situations. Upon completion of the
in oil field drilling. Sometimes diamond drill       hole, the steel casing is removed to be used
holes are cemented with quickset concrete            again, for it is very expensive.
under pressure, which is drilled back out as
soon as it hardens, leaving the hole clean and
free of fractures and caves. Sometimes it is
necessary to cement after almost every
                                                     Underground Exploration
advance of the bit in order to pass through             Only in rare instances is underground
troublesome ground.                                  exploration the prime method of proving a
                                                     prospect. A small, well-defined exploration
   Steel casing may also be set in the hole to       target such as a faulted segment of a vein might
eliminate caving and lost circulation, and to        be most efficiently explored by extending old
insure that a reliable core and sludgesample is      underground mine openings or from new work
obtained. By progressively reducing the bit          from the surface, but in general, a certain
size, and nesting the casing, each smaller size      amount of drilling is done first t o at least
inside the other, it is possible to carry casing     roughly outline the ore target.
fairly closely behind the drill bit. Diamond
                                                        Underground work is usually erroneously
cores commonly range in size from under 1 to 3
                                                     referred t o as tunneling. Tunnels are seldom
inches in diameter. It is possible to ream the
                                                     excavated i n mining, being a basically
smaller size holes out to accept larger casing,
                                                     horizontal opening from one side of a
and various combinations of drilling mud
                                                     mountain to the other, as in railroad and
cementing, casing, and reaming are used to           highway construction. The American metal
carry a hole to completion with the desired          miner refers to horizontal work into a hillside as
core size at the bottom of the hole.                 an adit (fig. 13). If the adit is driven along an ore
   In drilling vertical holes in porphyry copper     structure such as a vein, this is called drifting
prospects, it is common to cement into the           and the opening is referred to as a drift. If the adit
bedrock a short piece of casing called a             cuts across the wall rock at an angle to the
standpipe, just large enough to receive the          structure, it is called a crosscut and the work is
largest "Nu casing. The casing will in turn          referred to as crosscutting. The mouth of the
accept the NX diamond bit and core barrel,           adit opening is called the portal. Work upward
which cuts a hole 3 inches in diameter and a         from the adit level is called raising, and the
core 2-1/8 inches in diameter. NX bits are used      working is referred to as a raise. If the
to penetrate the leached cap rock over the ore       excavation is downward, it is called a winze.
deposit. As soon as the upper, enriched              Raises and winzes are usually in ore, although
portion of the sulphide zone is penetrated, "B"      the same terms are used whether the work is in
casing is set in the hole and the bit size           waste or in barren wall rock.
reduced to BX, which cuts a hole 2-3/8 inches           A shaft is a vertical or steeply inclined
in diameter and a core 1-5/8 inches in               opening excavated from the surface. The term
diameter. After passing through the upper            "inclined shaft'' refers to openings inclined
sulphide zone into unenriched ore, "A" casing        from vertical to 45" or less. When the
is set and the bit reduced to AX, which cuts a       inclination is gentle enough to accommodate a
hole 1-7/8 inches in diameter and a core 1-1/8       man on foot, rubber-tired equipment, or
inches in diameter.                                  conveyor belts, it may be referred to as a
                                    Figure 13.--Underground mining terms.




decline. Shafts, inclined shafts, or declines             laid on the floor before blasting to facilitate
may or may not be in ore.                                 shoveling or mechanical loading of the muck
   If work is undertaken underground from the             into wheelbarrows or mine cars and removal to
shaft, a station is cut as a landing for men and          the surface by tramming.
equipment, and horizontal work from the                      If some of the broken material removed from
station is by drifting or crosscutting, and is            the mine is known or suspected to be valuable,
referred to as a level in the mine. Work on any           it is placed on a separate dump. It is quite
mine level is generally inclined gently upward            common to find small dumps at exploration
away from the shaft station, so that any water            adit portals separated into two, three, or even
encountered will be drained toward the shaft              more separate portions. Careful sampling may
where it can be pumped to the surface or                  reveal little of value in the separated material.
diverted to an inactive portion of the mine.                 Small, ru bber-tired machines are now
   The methods and terminology used in                    available to load and tram from working faceto
exploration work are the same as in standard              portal, eliminating the need for rails in modest
mine development, but the openings are often              exploration programs underground.
driven in smaller cross sections to economize.               In formeryears, it was possible to find miners
They can later be enlarged if they are to be              skilled in the art of hand drilling or single
used for ventilating or draining a productive             jacking, the striking of hand steel with a short-
area, or in the movement of personnel,                    handled heavy hammer called a single jack.
equipment, or ore. Excavation is usually by               Such work could be done without air
drilling and blasting, although soft or highly            compressor, air lines, or heavy drills.
fractured ground may slowly yield to advance
by "pick and poke'' methods, using nothing but              Small, portable gasoline-powered drills have
a steel hand bar.                                         limited application in exploration work, and
   Drilling is done with pneumatic drills, and            there is constant danger of carbon monoxide
compressed air furnishes the power for the                even in the shallowest of excavations.
drill, provides air to the men at the working               Today there is a prejudice against
face, and moves powder smoke from the                     underground work as a prime exploration
heading after the blast. Holes are usually                method, and usually underground openings
blasted with stick dynamite and standard caps             are not thought of as exploration work.
and fuses. Electric blasting is sometimes used            Exploration is usually equated with drilling
as it is safer and is more efficient than spitting        from the surface, and any mention of
each fuse separately. The material broken at              underground openings suggests that the work
each blast from the face is called a round and            has somehow progressed to the development
the material itself referred to as muck. A muck           stage, and that the presence of ore is no longer
plate or slick sheet of flat steel is sometimes           in question.
           Bulk Sampling                              total storage area accommodates 2 or more
                                                      days of mine-run material.
   In most exploration work there is a need for
                                                        A portable crushing plant with a primary jaw
large, representative samples of the ore
                                                      crusher, secondary crusher, and a vibrating
deposit. A final cross-check of the grade of the
deposit must be made, as well as testing to           screen system produces a 1/2-inch mill feed
determine the best choice of metallurgical            product. Conveyors and transfer points are
method. Bulk sampling may also yield other            covered to reduce dust loss. The 1/2-inch
valuable data of use in planning mine and             product is sampled with a sample cutter
haulage facilities, the treatment method, or          producing 400 to 500 pounds per hour of
disposal of waste.                                    sample for testing. The material is fed to a
                                                      tertiary crusher producing a 1 0-mesh product,
  The mining characteristics concern such             from which a 5-percent "split" is taken. This
factors as the way the rock in an open pit mine       splitting procedure produces 20 to 30 pounds
may be expected to break during blasting and          per hour, which is bagged and sent for assay.
to support itself on a bench face, and the            The remainder of the crushed bulk sample is
manner in which the rock will cave in an              fed into a pilot plant.
underground b l o c k caving operation or
support itself in an underground mine.                  Samples obtained from most exploration
Metallurgical treatment methods can be most           drilling are not completely satisfactory in
effectively researched by p i l o t testing           preparing representative bulk samples. The
techniques, and disposal of waste can be              small samples are too finely ground by the drill,
carefully researched using the waste from             and in other ways rendered unreliable as a
these original testing programs.                      sample for investigation of breaking, handling,
                                                      and processing characteristics.
  Because of the large amount of material
                                                        Typically, large-scale bulk sampling is
required, bulk samples are usually collected
                                                      undertaken in the last stages of exploration of a
underground. The undesired surface chemical
                                                      low-grade ore deposit to be developed by open
and physical effects of weathering can be
                                                      pit methods. At one porphyry copper property,
avoided, and there is less p r o b l e m i n
                                                      a shaft was sunk on a centrally located portion
controlling fly-rock when large samples are
broken by blasting in confined underground            of the drilled-out deposit in mineralization
                                                      believed typical of the ore body. The shaft was
openings.
                                                      sunk directly on one of the exploration drill
   In most cases, bulk sampling produces a            holes, and all the material excavated was
larger volume of material than can be readily         collected as one hugh sample. A station was
handled. A temporary sample plant is                  cut in the shaft, several hundred feet below the
constructed at the site to reduce the size of the     surface at about the level of the lowest open pit
sample, yet retain its representative character,      mining planned. From the station, drifts were
particularly as utilized for a final check of grade   driven radially outward in a pattern resembling
and in pilot scale mill testing. It is sometimes      the spokes of a wheel, each drift directed
desirable to prepare a representative sample          toward an adjacent exploration drill hole. A
for prospective purchasers of the mine                raise was driven on each of these drill holes,
product.                                              using it as a pilot, to the surface.
   In a typical situation, the mine-run material,       The material from each of the raises was
blasted and mucked from individual rounds of          separately stored as an individual bulk sample.
underground advance in designated test areas,         Each sample was separately processed, and
is moved to a primary surface storage bunker          the grade of copper was analyzed as a check
with a 10- to 50-ton capacity. Each round is          against the assays obtained in the original
stored separately and assigned a lot number.          exploration drill holes. A very small upward
As each lot is removed by front end loader and        revision of the drill hole assays was indicated,
transferred to the crusher, the bunker is             lending confidence to the enterprise, and
carefully cleaned to prevent loss or buildup of       adding millions of pounds of copper to the ore
fine particles of the economic minerals. The          reserve available for mining.
                                                     underway, exploration continues as t h e
            Pilot Testing                            project geologist tests the various possible
   Preliminary metallurgical "bench tests" are       extensions of the ore body.
performed using a few hundred pounds of ore             Once the decision has been made to begin
from the drill core. The tests provide a general     development, the exploration geologist or
idea of the milling procedures to be used in         prospector, who has largely been responsible
concentrating the ore.                               for finding the ore body, leaves the scene. For a
   In a major project, underground bulk              variety of reasons, the exploration geologist or
sampling provides sufficient ore to operate a        prospector no longer contributes effectively to
pilot plant with a capacity of 50 to 100 tons per    the process of making the prospect into a mine.
day for several months. The pilot plant is a         Further geological work, drilling, or other
miniature version of the full-scale plant to be      operations to block out ore are done by a mine
built to concentrate the ore from the mine. The      geologist under the supervision of local mine
design of the pilot testing plant is based on        managers, who are, of course, production
knowledge of the type of ore in the deposit and      oriented.
the details of bench testing of ore from               The formal feasibility study includes an
exploration core drilling.                           economic analysis of the rateof return that can
  Details of crushing, grinding, concentration       be expected from the mine at a certain rate of
characteristics, and waste disposal can be           production. Some of the factors considered
studied over a period of time in a pilot plant.      during such an economic analysis are:
Also considered are the effects that a change in       Tons in the deposit
one part of the process will have on another, as       Grade of the mine product
well as the overall efficiency of the process.         Mill recovery
Alterations are made in the design of the full-        Sale price of the metal or mineral
scale plant. Costs of construction, operating          Cost of mining per ton
costs, and waste disposal problems can be              Cost of milling per ton
determined for use in broad planning and in            Royalties
the final feasibility study.                           Capital cost of the mine
   On a large project, the pilot plant work may        Capital cost of the mill
be done in a plant specially constructed at the        Exploration and development cost
mine site. In other cases, pilot test work will be     Mining rate, tons per day
done at a central company laboratory location,         Depreciation method used
university facility, or by metallurgical research      Depletion allowance
companies specializing in this work. The small         Working capital necessary
operator usually conducts pilot testing on a           Miscellaneous costs of operation
very small scale, and anticipates months of            Tax rate
modification of his full-scale plant to insure           In many cases this information will be put
good results.                                        through a computer to calculate the dollar
                                                     value of the yearly gross sales, operating costs,
                                                     o ~ e r a t i n a income, de~reciation. d e ~ l e t i o n ,
      Feasibility Studies                                          a,
                                                     income ; x net income after taxes, the cash
                                                     flow and the after-tax rate of return on
   At some point in the continuing exploration,      investment. Many companies have their own
it may become apparent that the program is           programs and computers. Outside firms are
successful--that an ore deposit is present.          available to undertake this work for a fee. Prior
  hen begins the work of bringing the ore body to    to the advent of computers, this information
its full potential by developing enough ore to       was laboriously calculated by a team of
plan a mining operation, or to completely            engineers using mechanical equipment
explore and develop the entire deposit.              requiring hundreds of computations and days
   In a typical feasibility study, all of the        0 weeks to complete the analysis.
                                                       ,
information gathered earlier is assembled and
turned over to an engineer or engineering              Each mining organization has a minimum
group for evaluation. While this study is            acceptable rate of return on investment. The
cost of borrowing capital for the mine or of       stockholders or investors to select projects
generating the needed capital internally within    with the best rate of return.
the company must be considered. If a                  As a general rule of thumb, a project must
company has a number o f attractive                have better than a 15-percent rate of return to
investment opportunities, the rate of return       be considered by a major company. An
from the proposed mine venture may be              individual commonly expects a 30- to 50-
compared with the rate expected on a different     percent rate of return to consider investing in a
mining venture elsewhere, or with some other       mining venture. Among other uses of the cash
business opportunity unrelated to mining. Every    flow generated by the mine, these funds must
organization has a limit to the amount of funds    finance continuing exploration elsewhere, pay
available for new capital investments.             for past failures, and contribute to the mine's
Management has an o b l i g a t i o n t o its      portion of main office and general overhead.




                                                             DEVELOPMENT                           I


  After exploration has provided a rough idea      ment planning because capital investment is
of the shape and size of an ore deposit, general   large, and mistakes are costly from this point
geological characteristics, and average grade,     onward.
and feasibility studies have thoroughly ana-          There are almost always small bothersome
lyzed the data available, the decision to devel-   details remaining at this point that should have
op the property may be made.                       been attended to prior to the discovery and
                                                   outlining of the ore deposit. For example, a
   At this time, the owner may decide to obtain    suitable millsite or townsite might not have
outside financing. Standard loan financing is      been secured, minor property ownership prob-
not often available to mine developers. The        lems may need to be resolved, or water rights
property may be sold outright for cash or for      may not be secured. For this reason, and the
stock in an operating company, or a royalty on     fact that entirely new personnel are sent
production may be retained. The owner of the       in to undertake development and may not be
new ore deposit may attempt to interest an         fully familiar with all aspects of the program,
operating group in furnishing management           company personnel are just as close-mouthed
and undertaking operation of the mine for a        as ever in dealing with outsiders.
percentage of the return. Often some form of         The various methods involved in mine
joint venture is worked out,when theowner of       development, and the emphasis given to them,
the ore deposit will agree to share the profits    depend to a large degree upon the kind of ore
after the mine has been put into production        body involved and the mining method to be
with an operator who is to provide the capital     used. Some of the more common approaches
and know-how to develop the mine. Even when        to mine development will next be described
the company develops its own exploration           to provide insight into this poorly understood
find, there is need for careful develop-           aspect of mining.
                                                    better designed and more elaborate
  Drilling Large Deposits                           than for exploration, because the equipment
   One or more stages of exploration drilling,      to be used is more complex and will be in
perhaps done over several decades, may reveal       operation over a longer period of time, and
the presence of a large body of what can now        work continues the year around except in
be called ore, considering present technology,      areas of extreme seasonal weather conditions.
economic conditions, and metal prices. The
entire deposit, or selected portions of it, may
now be drilled carefully to determine its exact
grade, volume, and three-dimensional outline.          Drilling Small Deposits
The development program should furnish the              If exploration of a small irregular deposit
following information:                              indicates the general position of the ore
   1. The size and shape of the ore deposit.        deposit in the subsurface, and if a high enough
   2. The average grade of the deposit and total    grade or large enough tonnage is indicated,
tonnage of material that can be called ore          there may be a trade-off decision whether to
within prescribed economic limits.                  undertake more drilling, perhaps using more
   3. The distribution of different kinds of ore,   precise methods, or to proceed directly with a
and the mineralogy of ores, if more than one        limited amount of underground development.
kind will necessitate separate handling or          T h i s usually depends more u p o n the
treatment.                                          philosophy of management than on the facts
   4. Geology of the ore body, particularly as it   that might be presented; some production and
will affect mine design and layout.                 exploration managers prefer to drill, and can-
   5. The location of waste rock which must be      not conceive of underground work for any-
selectively cast to one side or left unmined.       thing but production.
   6. Operating factors such as ground water,           Usually the decision to continue drilling is
nature of the rock as it may affect blasting or     made where costs are reasonable and there is
ripping characteristics, bench level intervals,     total confidence in the sampling procedures.
pit slopes, and need for secondary blasting.        If the deposit lies near the surface and can pro-
  The pattern and spacing development of drill      bably be mined by open pit, there is merit in a
holes requires special care because first           grid of vertical drill holes to exactly define the
preliminary ore reserve calculations are based      limits before stripping waste or attempting
upon the drill hole sample data. Some bulk          initial mine production.
minable types such as iron, coal, phosphate,            There are many cases where bold explor-
and potash usually have relatively uniform          ation drilling programs have been conducted
distribution. Low-grade copper or                   in areas of small, erratic, high-grade ore de-
molybdenum mineralization is much more              posits. In one such district in mountainous
erratic.                                            terrain, 10 relatively deep drill holes were put
                                                    down in an old silver district, and 3 of the holes
  Statistical techniques are important in plan-     intersected mineralization suggestive of the
ning development drilling programs, and in the      ore mined in the past, but at scattered local-
analysis of the sample data obtained. Enough        ities, at least 500 feet vertically, and 2,000 feet
holes must be drilled to insure continuity of       horizontally from any point where under-
geologic data between drill holes and to assess     ground development might begin. The costs of
the relation of geology to grade changes.           further drilling, of shafting, or driving an adit
   Where mathematical procedures have been          were all far more than any profit that could
used in determining the layout of develop-          reasonably be expected from an average ore
ment drill holes, it may be necessary to ad-        deposit in the district. The question in a case
here to a relatively rigid geometric pattern or     such as this becomes not so much "what do we
interval between drill holes, and this may          do with it?" as "why did we get ourselves into
require preparation of drill sites in posi-         this dilemma?"
tions that would normally not be considered,           As in all phases of prospecting, exploration,
at least in the initial phases of exploration       and development, the prime function of the
work. The drill roads and drill sites are often     project geologist is to have a clear picture of
the exact kind of ore sought, and the possible       ment work until after the mine is put into pro-
size and grade of the ore deposit as an eco-         duction. In this manner, capital investment
nomic entity.                                        requirements are offset as some financial re-
                                                     turn begins to come in. In the United States it
     Development Shafts                              is common practice to develop and produce
                                                     from the upper levels of a mine, and to later
         and Adits                                   deepen the shaft and develop the lower levels
    When the decision is made to do a certain        in a carefully planned schedule timed in co-
 amount of underground work as the first step        ordination with depreciation of the surface
 in mine development, it is essential to have the    plant. Usually some rule of thumb is adopted
 plan for mining worked out. In hilly or moun-       to insure that a ton of ore is developed for each
 tainous terrain, planning is less critical be-      ton of ore mined.
 cause a few short adits and a raise or two (fig.       At one property, a foot of development
 13) to the surface will inexpensively begin the     (drifts, raises, winzes) might be done for each
 development of the ore deposit and be of major      10 tons of ore taken from the mine. At another
value later in ventilation and in movement of        property a foot of diamond drilling per ton of
 men, equipment, ore and waste rock. If the          ore may be crude insurance that the develop-
terrain is relatively flat the decision to proceed   ment of the property is a viable operation.
 is far more critical, because shafting is very         The yearly statement of "ore reserves," if
expensive, and only a vertical shaft, well situ-     made available in any form to outsiders, there-
ated with respect to the ore deposit, will be use-   fore does not accurately reflect the possible
ful during later production work. If enough          ultimate production of the mine. There are
data are not available to plan such work, one        many reasons for such conservative practices;
might seriously ask if exploration information       abrupt fluctuations of metal prices can convert
 is sufficient to proceed with development.          ore to waste overnight, local tax laws may be
    It is not uncommon for mines to go through       applied on an "inventory" basis to a wasting
two or more stages of development and re-            asset, labor negotiations can become difficult
development. A relatively modest shaft and           if there is a false impression as to longevity of
hoisting facility might be entirely adequate to      the operation, and there would be legal ques-
develop and mine 100 tons of ore per day in          tions introduced if speculative material were
relatively rich material near the surface. After     called ore by management.
several years, long-term plans may indicate the         When a miner speaks of production plus re-
need for a much larger headframe and hoist,          serves, he is making little allowance for ore
when development of large tonnages of low            that lies far ahead of present development
grade ore deeper in the mine makes possible          work. Some companies have only a certain
a production rate of 1,000 tons per day with a       minimum tonnage of reserves on hand, and do
new and larger mill on the property. The smaller     not feel the cash required to increase the re-
operation may have financed the major de-            serve figure is a good investment. Three cate-
velopment work, and proven the larger ore re-        gories of ore--proven, probable, and possible--
serve far more thoroughly than any exploration       are generally accepted in statements of ore
work that might have originally been justified.      reserves (fig. 14).
Usually these redevelopments are not inten-
tional but are the result of higher metal prices,          Proven (Measured) Ore
unexpected good results in initial develop-
ment, new milling methods becoming avail-               Proven ore is that for which tonnage is com-
able, or other factors.                              puted from dimensions revealed in outcrops,
                                                     trenches, workings, or drill holes, and for
                                                     which grade is computed from adequate sam-
        Blocking Out Ore                             pling. The sites for inspection, sampling, and
                                                     .   -                                -   -
          Underground                                measurement are so closely spaced, on the
                                                     basis of defined geological character, that the
  In a typical underground operation, it is          size, shape, and mineral content are well
desirable to postpone some of the develop-           established.
               leached zone



              proven ore



              probable ore



              possible ore



              stope
                 broken ore


              stope f i l l




                              Figure 14.--Partially developed vein, three ore categories.


     Probable (Indicated) Ore                                 include comparison with deposits of similar
                                                              types. Bodies that are completely concealed,
   Ore for which tonnage and grade are com-                   but for which there is some geological evi-
puted partly from specific measurement, sam-                  dence, may be included.
ples, or production data, and partly from pro-                   The terms proven, probable, and possible
jection for a reasonable distance on geological               are used by mine operators to distinguish the
evidence is considered probable ore. The                      ore categories in a single mine or perhaps, at
openings or exposures available for inspec-                   most, a mining district. Locally, much more
tion, measurement, and sampling are too                       rigorous definitions of proven, probable, and
widely or inappropriately spaced to outline the               possible are used. The terms measured, indi-
ore completely or to establish its grade                      cated, and inferred are applied in a much
throughout.                                                   broader sense, such as in expressing the re-
                                                              serves of the bedded phosphate ore in a wes-
                                                              tern State, and are employed mostly by Federal
     Possible (Inferred) Ore                                  and State agencies, mineral economists, aca-
                                                              demicians, and commodity analysts.
  Quantitative estimates of possible ore are
based largely on knowledge of the geological
character of the deposit and few, if any, sam-
ples or measurements. Estimates are based on
                                                                                    Access
assumed continuity or repetition for which                      Because of the heavy flow of traffic and large
there is geological evidence; this evidence may               equipment involved, the requirement for good
access roads is generally greatest during mine       contracts with power companies and public
development. Many western States and coun-           utilities for new transmission lines and sub-
ties move construction and maintenance of im-        stations necessary to bring outside power into
 proved roads into a position of first priority in   the property. At smaller properties, or those in
their budgets, especially where a good road          very remote locations far from low-cost sourc-
can be easily constructed from one of the             es of electricity, diesel generator sets are in-
county's towns directly to the mine. The coun-       stalled within the mine-mill plant complex. The
ty then not only receives the tax benefits pro-      principal considerations are a site suitable for
vided directly by the mining operation, but also     unloading and storage of bulk fuel, distance of
retains the much larger secondary benefits of        transmission of power, and position of the
commerce and employment and tax revenues             plant away from residential areas because of
from them. The tremendous economic impact            the noise.
of a new mine operation is often not fully ap-          Energy for the powerplant is usually derived
preciated by economists and land use planners        from water or hydrocarbon fuels in typical
more accustomed to dealing with agriculture          mining situations. The diesel-engine generators
or normal urbanization, and the financial im-        especially adaptable to smaller locations have
pact may come as somewhat of a bombshell to          outputs up to 15,000 to 20,000 kilowatts and
local planners.                                      can be preengineered by manufacturers to
   The access roads to a property being de-          company specifications. Steam generating
veloped by underground methods are often in          plants generally have a minimum economic
canyon bottoms and stop at the site of the main      output of 5,000 kilowatts. Where public utility
shaft of adit portal on the main development         or Government power is available, the mine
level. Additional roads over the surface of the      owner usually finds it cheaper and more re-
ore deposit are not usually necessary, except        liable than generators, and he will share in the
to service ventilation equipment in a second         cost of constructing the connecting line from
exit or for other service functions specific to      the closest existing utility line. Up to a con-
the site.                                            nected load of about 1,000 horsepower, it is
   Where large deposits are being developed by       cheaper to let the utility provide a primary sub-
drilling and open pit methods are planned,           station; above this horsepower a more favor-
building access roads for drills is a major un-      able rate may be obtained by constructing a
dertaking, and surface disturbance is at a max-      private primary substation to transform in-
imum, especially in the area immediately over        coming power to usage voltages.
the ore. These roads can be extremely un-
sightly because they are so closely spaced and
often traverse steep hillsides where no normal
road would be planned. They will be removed                  Communications
during stripping and mining or will be covered         At most locations, entry into the develop-
by waste dumps placed around the pit as de-          ment stage calls for planning full telephone
velopment and production continue. In gen-           communications for the mine and mine com-
eral, the access roads on private property will      munity. In the western United States, mine
be paid for entirely by the mining company,          operators are not as aviation conscious as in
although they may be later opened to provide         similar areas of Alaska or Canada, but some
access for the public to recreational areas,         thought is usually given t o a small landing
vistas of the mine operation, or other areas of      strip or helicopter landing area for direct air
general interest.                                    evacuation of seriously ill or injured personnel.
                                                       As development continues, limited medical
                  Power                              facilities are constructed, but the nature of
                                                     mine and mill industrial accidents is such that
   The requirement for electricity in mining         immediate air or other rapid evacuation of
operations is usually large from the develop-        victims is contemplated to the specialized
ment stage onward where essentially all power        medical facilities available only in the larger
is electrical except for mobile units, such as       communities. Many companies maintain com-
trucks. Large developments usually involve           pany-owned ambulances or enter into con-
tractual or cooperative agreements with others                   The mine plant must be suitably situated for
for ambulance service.                                        access by road. The ground beneath must be
                                                              suitable for support of building foundations,
                                                              and the area should be free from risk of land-
         Site Preparation                                     slides, avalanches, or unusual runoff during
                                                              the various flood seasons.
   The location of the ore deposit determines
the mining method, and once the choice is                        The basic mine plant for underground min-
made, the siting of surface facilities is a rela-             ing operations consists of headframe, hoist,
tively inflexible analysis or checkoff to deter-              timber framing and storage area, miner's
mine which location best meets requirements.                  change house, compressor house, machine
                                                              shops, warehouse, office, ore storage, and ore
                                                              loading and shipping facilities. In unusually
                                                              severe topography, the ore may be hauled by
   If a vertical shaft is to be the main develop-             truck, conveyor, or aerial tramway t o the treat-
ment, it may be desirable to sink it in barren
                                                              ment plant, and coarse crushing may be done
wall rock at one end or to one side of the ore de-
                                                              at the mine. Normally the ore treatment plant is
posit to keep haulage and hoisting facilities
                                                              placed as close to the mine as possible to re-
clear of actual underground mining, yet mini-
                                                              duce handling, and in some cases to facilitate
mize tramming of ore underground to the mine
                                                              return of the mill tailings underground as fill to
exit. Inclined shafts and declines allow a mea-
                                                              support stoped areas (see fig. 13, 15).
sure of flexibility, for they can be directed from
a suitable surface point t o the ideal position                  In many underground mining situations, the
underground.                                                  surface plant can be located directly over the
  Horizontal development by adit is the most                  mine without fear of damage due to subsi-
difficult to plan in some respects, and is usually            dence. Where large amounts of development
considered only where topographic relief is                   must be done in barren wall rock, and the re-
considerable. Development by adit is prefer-                  sulting waste cannot be disposed of in cut-
able because water can be drained without                     and-fill stopes, it is necessary to provide for
pumping, and level ore haulage systems re-                    waste dumps near the collar of the shaft or por-
quire far less energy and capital investment                  tal of the adit.
than hoists over shafts or conveyor systems in                  In open pit operations, large areas are re-
declines. Also, the ore and waste can be taken                quired for roads, mining, stripping, disposal of
down and out of the mine at minimal operating                 waste rock, and low-grade stockpiles or heap
cost.                                                         leaching operations.




             S e c t ion A-A'
                                 A\




                                         b   r    'A'



                                                 shaft

                                  Plan
                                                                             Sect ion B%'


                                  Figure 15.--Open stope mining method.


                                                         52
   Extensive parking areas are required if the                        Townsite
employees travel to work by automobile. When
space is restricted, remote parking areas are          Whenever possible, mine planners try to
serviced by shuttle buses to take the men to the    avoid getting into the business of providing
working area. If the mine is in a very remote       housing, public buildings, streets, schools,
region, temporary housing and meal facilities       and playgrounds. They will make every effort
may be provided for visitors, maintenance           to utilize and expand existing facilities in near-
personnel, and top management.                      by towns. The idea held in former years that
  An effort is usually made to locate and con-      an additional profit could be made from the
struct the mine plant in harmony with the local     company store and other tightly controlled
environment, but safety and fire insurance          facilities has given way to an open attitude
considerations may dictate a certain amount         where the company will help support local
of careful clearing of forest around the surface    schools, trailer parks, and medical and other
installations so that they may be protected         facilities, with private individuals or independ-
from forest fires. This also minimizes the risk     ent groups responsible for their operation.
of igniting the surrounding forest if a fire           Where a town is built for company per-
starts within the plant.                            sonnel, suitable space must be provided for a
   In extremely difficult surface situations,       small city in no way different from a mature
mine plants, and in a few cases the ore treat-      community, except that all applicable build-
ment facilities, have been installed under-         ing codes will necessarily be adhered to and
ground as a more economical measure than            the facilities~commonly     serve a larger propor-
attempting t o combat steep terrain, bitter         tion of younger families. The townsite may be
low winter temperatures, or risk of avalanches.     close to mine and mill, so close that the aver-
Today much consideration is given to locating       age employee can walk to work. The housing
the surface mine plant in some side canyon          provided for families usually is an added cost
away from public view, even if this may involve a   of the operation, but living facilities for un-
longer haul for ore and waste and extended          married workers may come much closer t o
access roads. With planning and a slight            breaking even financially. North American
additional investment, it might be possible         mining communities average about' five per-
to have the entire mine operation out of sight      sons per family, and the ratio of married to
of the average tourist.                             single employees varies depending upon the
                                                    isolation of the project.
                                                       In extremely remote situations, unusual
                     Mill                           schedules are established so that employees
   In former years, mills were generally            work relatively long shifts for short periods,
constructed on hillsides to utilize gravity to      with high wages and frequent short vaca-
feed ore and water through the plant. Today,        tions, and free transportation home to their
construction costs and workers' demands             families and back. At the mine, bachelor facil-
favor construction of mill facilities on about      ities are provided for all workers. The opera-
the same level as the mine. The mill is situated    tion is expected to yield a higher than normal
at some convenient site between the mine and        return on investment to offset these increased
the mill tailings disposal area. The main offices   labor costs.
and powerplant are usually located at the
mill, where mine and mill are separated.
   Ore crushing, blending, and storage units                Postponement of
must be accommodated, as well as €he mill
structure itself and warehouses, loading,
                                                              Production
unloading, and weighing facilities. Loading           Sometimes, after the excitement of the orig-
and turnaround facilities for trucks and rail-      inal land acquisition and exploration drilling,
roads may be a major space requirement,             work on a mine project is halted. This is
where large amounts of ore or concentrate           perplexing to local people, some of whom may
are shipped or large quantities of mine sup-        have begun to make changes in their personal
plies and mill reagents are received.               and business lives in anticipation of the new
mining operation. There are many reasons             immediately, and some of the more critical
why a mining company may delay putting               ones are completely beyond the control of the
property into production. There are always           company:
rumors going around when this happens, and               1. Drop in price of mine product, or no rise
business people and community leaders                in price if this had been anticipated.
sometimes call for a clear statement of intent,
                                                        2. Increase in labor costs.
so that everyone will know what to expect.
                                                        3. Unfavorable legislation or regulations.
  Sometimes it is possible t o make such state-         4. Change in tax laws or assessment pro-
ments, and periodic updates may be issued in         cedures.
the interests of community relations. Just as           5. Threat of litigation.
often, company management has been so                   6. Action of private conservation groups.
taken aback by an unforseen or uncontrollable           7. Lack of smelter or refinery capacity.
event, or series of events, that they do not            8. Lack of capital.
know what the best plan for the future might            9. Delay in obtaining delivery of major
be. Rather than issue a false statement, or          equipment.
speak in generalizations tantamount to false-          10. Lack of transportation facilities.
hood, the company may choose, or be advised,
to remain silent. The local project manager            Although oneor two of these considerations,
sometimes has no authority to discuss the            or similar ones, may be the paramount reason
future of the project, and a meaningful state-       for postponing development of the mine, there
ment can only be obtained from higher man-           are usually many other factors involved, and
agement.                                             the "go" or "no go" decision is carefully weigh-
   Although there are cases when a company           ed against a list of favorable and unfavorable
may decide to delay further development,             factors, some of which may be changing while
it is not usually advantageous to do so. A con-      the deliberation is being made.
siderable capital investment must then lie              From the standpoint of surface damage to
idle, providing no income. Such items as the         the environment, it is particularly unfort-
wages of standby personnel and watchmen,
                                                     unate when the property must be put into a
costs of insurance, taxes, minimum payments
                                                     holding situation. Often, considerable damage
on property, and assessment work on claims
                                                     has already been done during the exploration
add up to a major expense and accomplish
                                                     and development stages, and it will remain
nothing productive. The morale of project per-
                                                     until the decision to mine is eventually made.
sonnel is also a consideration; professional
                                                     For example, an ore deposit near the surface
staff prefer to be associated with a live project,
                                                     that is to be mined by open pit methods will have
where a sense of accomplishment can be
                                                     been drilled in a close-spaced pattern of
gained from the day-to-day activities of a suc-
                                                     vertical holes and the close network of access
cessful operation. To the individual pro-
                                                     roads over the property will usually have made
fessional person, assignment to a dormant
                                                     a mess of the surface, particularly from the
project often translates into a dormant pro-
                                                     visual standpoint. There are many people who
fessional career.
                                                     find nothing particularly ugly about a well-
   Some typical reasons why a company may            engineered and smoothly running open pit
decide to delay production are: (1) A portion        mining operation; however, no one would view
of the mining property, water rights, surface        the drill roads as anything but an eyesore.
rights, or other legal rights still has not been
acquired; (2) better market conditions may be          Although some properties have lain idle for
anticipated; (3) equipment or personnel may          years or even decades, most economically
be coming from other operations; (4) an as-          marginal mining properties will someday be-
sortment of unrelated problems might best be         come minable. Increased efficiency of mine
solved by simply waiting them out.                   and mill equipment and increases in metal
                                                     prices gradually lower the economic "cut-off"
  Many and varied are the reasons why a com-         grade for ore over the years, and marginal
pany cannot put the property into operation          properties eventually are developed.
                                                                  PRODUCTION                            1




   Prior to development of an ore deposit, the       after open stoping a mine, the pillars are "rob-
exact choice of mining method will have been         bed" just before abandoning that portion of the
made. The type of haulageway for one mining          mine, and the collapse of the stope walls is of
method might be totally unsuitable for another       no concern to the operation. Sometimes nar-
method, and it is necessary to plan for produc-      row veins can be open stoped, placing an oc-
tion from the very beginning. Underground            casional wood stull, or wood beam, from one
methods of mining are called stoping by the          wall of the stope to the other. This is called stull
American metal miner, and are particularly           stoping. The stulls serve to support the vein
varied.                                              walls, and as places to anchor wood platforms
                                                     upon which the miners and equipment stand
                                                     while drilling ore overhead.
          Underground                                   Room and pillar mining (fig. 16) is commonly
                                                     done in flat or gently dipping bedded ores.
         Mining Methods                              Pillars are left in place in a regular pattern while
   The various stoping methods have evolved          the rooms are mined out. In many room and
over the years to cope with particular condi-        pillar mines, the pillars are taken out, starting at
tions or to take advantage of certain kinds of       the farthest point from the mine haulage exit,
labor, equipment, or new techniques as they          retreating, and letting the roof come down up-
become available. In selecting the most appro-       on the floor. Room and pillar methods are well
priate stoping methods, the size and shape of        adapted to mechanization, and are used in de-
the ore body is the most important consider-         posits such as coal, potash, phosphate, salt,
ation. Overburden conditions, strength of ore        oil, shale, and bedded uranium ores.
and enclosing wall rock, water, value of ore,
and other factors must also be taken into ac-
count. Although there are minor variations or                  Shrinkage Stoping
modifications of most of the stoping methods,
it is usually possible to clearly identify the          Shrinkage stoping (fig. 17) is done by stop-
basic method in use at a given mining                ing the ore deposit from beneath, allowing
operation.                                           broken ore to support the stope walls, but
                                                     leaving a space above the broken ore just suf-
                                                     ficient for the miners to stand on and drill over-
              Open Stoping                           head. Broken ore is drawn as necessary to
  Small ore bodies are often mined completely        maintain this headroom, and because the vol-
out, leaving no pillar of ore in place t o support   ume of rock expands upon breaking, about a
the walls of the stope. In some kinds of rock, it    third of the broken ore is drawn from beneath
is possible t o mine out huge stopes which           as stoping progresses from the bottom of the
stand open (fig. 15) for years.                      ore block to the top.
  Where some of the ore body is left in place as        After the stope is completed, all broken ore is
random pillars to support walls, the material is     removed and the walls are allowed to cave in.
low-grade wherever possible because it may           The wall rock must be strong enough to sup-
never be removed from the mine. Sometimes,           port itself during shrinkage stoping, without
                                Figure 16.--R00m and pillar mining method.


breaking away and becoming mixed with the                 stope walls and to serve as a platform for
broken ore. Steeply dipping veins with well-              miners and their equipment. All ore is taken
defined, hard walls are most suitable for                 from the stopes as it is mined, through tightly
shrinkage stoping.                                        timbered raises up through the fill, called ore
                                                          chutes. Broken waste rock is commonly used
         Cut and Fill Stoping                             for fill and usually comes from development
  The development work for cut and fill stop-             headings elsewhere in the mine. This practice
ing is similar to that for shrinkage stoping, ex-         makes it possible to dispose of waste rock
cept that as each cut of ore is removed, a layer          underground without the expense of hoisting it
of waste is placed in the stope to support the            to thesurface for dumping.




                                      Figure 17.--Shrinkage stoping.


                                                     56
                                                                                   and   c




                                       Figure 18.--Hydraulic stope fill.




   A variation of the cut and fill stoping meth-                       Square-Set Stoping
ods involves returning carefully sized mill
tailings in a slurry to the stopes underground,              The square-set method (fig. 19) is used
where the slurry is hosed into place as stope fill         where the ore is weak, and the walls are not
under the pressure developed by the head.                  strong enough to support themselves. The
Water quickly drains from the tailings fill,               value of the ore must be relatively high, for
which becomes compact enough to support                    square-setting is slow, expensive, and requires
the weight of men and equipment as they con-               highly skilled miners and supervisors. In
tinue to stope overhead. This method is refer-             square-set stoping, one small block of ore is re-
red to as hydraulic filling (fig. 18) or sand fill         moved and replaced by a "set" or cubic frame
mining and is a convenient way of combining                of timber which is immediately set into place.
the solutions to the stope fill and mill tailings          The timber sets interlock and are filled with
disposal problem.                                          broken waste rock or sand fill, for they are not
                                                           strong enough to support the stope walls. The
   Rill stoping is cut and fill stoping where the
                                                           waste rock or sand fill is usually added after
slices are inclined to the horizontal, so that ore
                                                           one tier of sets, or stope cut, is made.
moves down out of the stope, and waste slides
down into the stope from above, without the
need for hand shoveling or mechanical scrap-
                                                                           Block Caving
ing. Cut-and-fill stoping methods are used                   The block caving method (fig. 20) is used in
where one or both walls may be weak, so that               mining large ore bodies that have a barren or
they would collapse into the stope to mix with             low-grade capping too thick to strip away from
broken ore if not carefully supported.                     the surface. In development, evenly spaced
                                              raise


                                                                                         -fill
                                                                                         -ore

                                                                                         floor
                                                        Vertical     sectton

                                                                          blocLin~

                                                                                            corner set
                                          lead s e t

                                                                                           .ore




Square-set r imbering                                  Plan of a m i n i n g f l o o r


                           Figure 19.--Square-set stoping.




                        Figure 20.--Block caving underground.


                                         58
crosscuts are made below the bottom of the           be processed. Most surface deposits rich
ore block to be caved, from which raises are         enough to be mined and concentrated by pan-
driven up to the ore. The entire ore block is        ning were worked over long ago, in many cases
undercut so that it will begin caving into the       by Chinese workers left idle after the construc-
raises. The weight of the capping and ore pro-       tion of the transcontinental railroad. With to-
vides the force to crush and move the ore            day's high wages and employment opportuni-
downward, where it is drawn from the raises          ties, the deposits remaining are far too low
beneath, trammed to the shaft or decline, and        grade to be worked on a sustained economic
hoisted to the surface.                              basis. The gold pan is now used mainly as a
   As broken ore is removed, the capping will        tool in prospecting and exploration of low-
gradually descend until broken fragments of it       grade placer deposits being considered for
coming from the raises indicate that all of the      bulk mining methods such as dredging.
ore has been withdrawn. The surface over the             In recent years, gold panning has become a
worked-out mine is a gigantic collapse feature,      popular outdoor recreation. There is excite-
not as deep as the height of ore withdrawn, be-      ment and appeal in panning an occasional
cause of the "swell factor" of the broken cap-       nugget or a few small specks of gold. The re-
ping, but considerably larger in diameter than       mote chance of discovering a rich pocket
the area actually caved underground.                 somehow missed by the oldtimers provides a
                                                     stong incentive. In general, far more money is
          Surface Mining                             made selling manuals, maps, equipment, and
                                                     gas and oil to these hobbyists than is made
             Methods                                 from the gold itself. There are shops along the
  Because of the rapid development of many           foothills of the Sierra in California where small
types of large and efficient earthmoving ma-         quantities of placer gold are sold at great mark-
chinery and auxiliary equipment, surface min-        up over metal market quotations, so that the
ing methods have made it possible to mine            unlucky weekend gold panner need not return
many ore deposits that would be uneconomic           home emptyhanded.
to develop underground. Although there is               In sluicing, the placer gravel is shoveled into
great variation in detail, only a few basic met h-   the head of an elongated sluice box which is
ods are employed, and the terminology is             inclined and has various configurations of bars
much more simple than in underground                 and traps across the bottom called riffles.
mining.                                              Water is directed through the sluice box, and
              Placer Mining                          the heavy placer minerals are trapped in the
                                                     riffles; the fine material is washed over them
   Placer deposits are concentrations of heavy       and out as a relatively barren tailing. Few de-
minerals, usually within loose alluvium that         posits are left unmined in the western United
can easily be excavated and washed. Placer           States, where sluicing might be economical at
minerals such as gold, tin, and tungsten min-        present gold prices.
erals, are of relatively high value, but the value      In both panning and sluicing operations, it is
of the placer gravel itself may bevery low, often    sometimes possible to collect very fine parti-
less than a dollar per cubic yard. For deposits      cles of gold by amalgamation, when mercury is
of such low grade to be worked they must be          either placed in the bottom of the riffles or
near water, on or near the surface of the            smeared on copper plating. The fine gold
ground, and should be only loosely consoli-          amalgamates with the mercury and is collected
dated so that drilling and blasting are not nec-     by retorting in small devices which drive off the
essary. The bulk of placer mining falls into         mercury as vapor, retaining the gold.
three groups--panning and sluicing hydrau-              Hydraulic mining.--In hydraulic mining, or
licking, and dredging.                               "hydraulicking," a stream of water under great
   Panning and sluicing.--The traditional gold       pressure is directed against the base of the
miner's pan is an efficient device for washing       placer gravel bank using pipes and large noz-
and separating placer minerals. However, the         zles called giants. The water caves the bank,
method is slow, and even in the hands of askil-      disintegrates the gravel, and washes the bro-
led operator only small volumes of material can      ken material to and through sluice boxes situ-
ated in convenient positions downslope. Hy-               surface, and perhaps even to improve some as-
draulic mining totally disturbs large surface             pects of the floodplain or nearby river channel.
areas, puts much loose debris into the drain              It is not possible t o restore the land to the pre-
age system, and involves large surface water              cise original contour, for the swell factor of the
runoff that may cause substantial damage                  gravel increases volume 20 percent or more. In
downstream. Many of the western States pas-               many areas in the West, particularly near major
sed laws years ago to closely control "hy-                construction projects or cities, clean gravel
draulicking," and few substantial deposits of             placer tailings are valuable for manufacture of
placer gravel remain that could be mined eco-             aggregate, or crusher run, in fills of various
nomically w i t h i n t h e restraints of this            kinds, and can be considered a resource in
legislation.                                              their own right. In a few areas, peopletraveling
   Dredging.--Large alluvial deposits are mined           through areas of old placer tailings, expecting
by floating washing plants capable of excava-             the area to be some sort of wasteland, are
ting the gravel, processing it in the washing             pleased to find a great variety of fishing and
plant, and stacking the tailings away from the            water sport recreation available, and thriving
dredge pond. Two kinds of equipment--bucket               wildlife in the habitat that has been created.
line and dragline--have been used. The bucket                Because large placer deposits can be thor-
line dredges are larger and more efficient, con-          oughly explored before floating the dredge,
sisting of a continuous line of buckets that              such operations lend themselves to thorough
scoop the material from the gravel bank at the            planning, and it is possible to do a consider-
edge of the dredge pond, raising it to the top of         able amount of reclamation at only slight in-
the washing plant mounted in the hull. Drag-              crease in overall operating costs.
line dredges are smaller and less efficient, and
employ a single bucket that digs the gravel and
is swung over the feeder hopper of a floating
                                                                          Glory Holing
washing plant similar to the layout in a bucket             Almost every opening at the surface is refer-
line dredge, although usually smaller.                    red to by local writers and mining buffs as
   Dredging temporarily involves total disturb-           "glory holing" (fig. 21). Actually this kind of
ance of the ground surface, although with                 operation is uncommon, as it involves a mine
careful planning and engineering of theopera-             opening at the surface, from which ore is re-
tion it is possible to plan for restoration of the        moved by gravity through raises connected to




                                   Figure 21.--The glory hole mining method.


                                                     60
adit haulageways beneath, and by tramming                 "oxide" ore must be treated by acid leach, but a
the ore to the surface on the haulage level.              second kind of "sulphide" ore must be treated
   The glory hole method is best suited to min-           by different methods.
ing on a hillside, and irregular deposits can be
cleanly mined without dilution by waste wall                 The grade and tonnage of material available
rock. Narrow veins have been mined by glory               will determine how much waste rock can be
hole; in these cases the "hole" becomes narrow            stripped, and there is often an ultimate limit to
and long. The benches are mined away as work              the pit that is determined more by the eco-
descends to the bottom of the deposit or to the           nomics of removing overburden than asudden
haulageway, so that spectacular steep side-               change in the ore deposit from mineral to non-
walls may result if the walls do not slough in.           mineral bearing material. The ultimate pit limit
Mining can be quite selective, and little waste           and the slope of the pit walls are therefore de-
rock is thrown on the surface dumps. The prin-            termined as much by economics and engineer-
cipal environmental objection to the method is            ing as by geological structure. Material that is
difficulty in reclamation of the surface of the           relatively high grade may be left unmined i n
mine area.                                                some awkward spot extending back too deeply
                                                          beneath waste.
            Open Pit Mining                                  The typical large open pit mining operation
   Although the basic concept of an open pit              that has been in production for 10 years and
(fig. 22) is quite simple, the planning required          more is operating under conditions that could
to develop a large deposit for surface mining is          not possibly have been foreseen by the original
a very complex and costly undertaking. In one             planners of the mine. Metal prices, machinery,
mine, it may be desirable to plan for blending            and milling methods are constantly changing
variations in the ore so as to maintain, as nearly        so that the larger operations must be period-
as possible, a uniform feed to the mill. At an-           ically reevaluated, and several have been com-
other operation it may be desirable to com-               pletely redeveloped from time to time as en-
pletely separate two kinds of ore, as for exam-           tirely different kinds of mining and milling
ple, a low-grade deposit where one kind of




                                        Figure 22.--Open pit mining.


                                                     61
   Sometimes the preliminary stripping of the        Subsidence it desirable, because it increases
waste overburden is contracted to firms spe-         the solution of mineral, and destroys voids,
cializing in earthmoving. Mining is usually          reducing the amount of solution required and
done by track-mounted electric shovels in the       the time needed for it to act.
large operations, and by rubber-tired diesel           In applying methods of solution mining t o
front-end loaders in the smaller operations.        traditional ores such as the base and pre-
Scrapers are sometimes used in special situ-        cious metals, subsidence will not be as important
ations. Large bucket-wheel excavators of the        as surface disturbance, for the metal taken into
kind used in European coal mines have not           solutions is only a minute portion of the total
been applied to metal mining, because this           rock matrix. It has been suggested that some
equipment is best adapted to softer bedded,         zones of low-grade mineralization might be
relatively flat-lying strata.                       leached in place, and there is particular inter-
   Haulage is usually by truck, although rail-      est in copper and gold ores, which have long
roads, inclined rails, and conveyor belts have      been leached using "vat" processes and urani-
been used. The conveyance unloads directly in-      um, which is easily taken into solution in a
to a primary crusher and crushed material is        number of solvents.
stored in coarse ore bins prior to shipment to         Biologic activity is known to hasten the
the mill.                                           conversion of metal in many ores to a more
   Bench level intervals are to a large measure     soluble form. Several naturally occurring
determined by the type of shovel or loader          bacteria have been found to oxidize such
used, and these are selected on the basis of the    insoluble minerals as copper sulphides,
character of the ore and the manner in which it     increasing solubility a thousandfold over the
breaks upon blasting and supports itself on the     sterile condition.
working face. Blastholes are usually drilled           A great deal of research is being done t o
vertically by self-propelled, track-mounted         determine the conditions most favorable for
pneumatic or rotary drills. Bulk explosives are     good solution of metal, and the method can be
loaded in the holes and large volumes of ore        expected to contribute significantly in future
are broken in asingle blast. Sometimes the drill    mining operations, if not become an important
holes are routinely sampled and assayed to          mining method in its own right. Operators are
help plan the position of theshovels in advance     particularly watching developments of new
of mining. Blasthole assay control is especially    organic solvents that are environmentally
desirable when exploration data are incom-          acceptable, are specific for the element
plete or lacking as in the case in the older pits   desired, and do not react with or become
which have long been mined past the limits of       consumed by wall rock.
"ore" used in original planning.                       The methods most commonly used for
                                                    distribution of leach solution are flooding
                                                    ponds over the leach dump, spray, trickle, and
                                                    solution injection. The pregnant solutions are
          Leaching Methods                          collected beneath the leach zone and are
   Solution mining techniques are used for          pumped t o precipitation plants nearby or to the
extracting soluble ores such as potash and salt     precipitation section of the main ore treatment
in situations where conventional mining             plant where this is feasible.
methods would not be economic. Total solu-             In-Place Leaching.--Because the natural
tion of all the mineral is not always accomplish-   porosity of most rocks is too low for rapid,
ed. Sulfur is mined by the Frasch process,          pervasive penetration of leach solutions, it is
using steam to melt the sulfur and bring it to      necessary to fracture the rocks artificially.
the surface through bore holes. The future of       Conventional explosives have been used, and
solution mining appears promising, for there is     one low-grade copper deposit in Arizona is re-
constant improvement in equipment, solvent,         peatedly suggested as a likely place to research
and in technology of breaking rock in place         underground use of a nuclear device, where
and controlling the movements of fluids             breakage, heat, and pressure would combine
through it. In mining salt, potash, and sulfur,     to make the copper sulphide minerals much
the overburden and surface over it subside.         more soluble than in ambient conditions.
  On a more limited scale, in-place leaching          cannot be treated economically by conventional
has been applied to fill in old mine stopes,          processes may be mined and heap leached.
caved areas over block caving operations              The techniques are no different than for
underground, and in peripheral portions of            leaching mine dumps, except that t h e
conventional open pits where the grade is too         operation is totally planned, and the precipita-
low to permit mining the material.                    tion plant is often specifically designed for the
                                                      purpose, rather than being a section of the
  This method is not well enough understood,          plant at a conventional metallurgical
nor has enough experience been gained to              operation. Heap leaching has been applied
apply it to avirgin, high-grade ore deposit with      mainly to low-grade copper and uranium min-
assurance of control and predictable recovery         eralization, although t here is presently much
of values being leached. The method holds             interest in the method for precious metals.
great promise, because capital costs are low
and there are fewer environmental problems
compared to the movement of vast tonnages of
rock in conventional mining.
                                                                 Ore Dressing
                                                         At most modern mining operations, whether
   Mining Dumps.--Low-grade copper mines              surface or underground, the ores are not rich
usually employ some form of leaching for              enough to ship long distances to smelters, and
recovery of small amounts of copper contain-          they are subjected to milling, mineral dressing,
ed in overburden and waste. Open pit gold             or beneficiation. All of these terms are some-
mine operators have begun to follow this              times referred to as ore dressing. Ore dressing
practice, particularly where the pregnant             is the mechanical separation of the grains of
liquor can be pumped to the precipitation sec-        ore minerals from the worthless gangue. The
tion of an existing metallurgical plant. Usually      resulting concentrate contains most of the ore
no special consideration is given to the              minerals, and the waste is called tailings.
preparation of the mine dump for leaching, and
in fact the decision to leach often comes after         Crushing and Concentration
the dump was laid down. Where it is possible to
plan ahead for leaching, t h e f o l l o w i n g         Usually two stages of crushing are used in
operations are standard practice:                     ore dressing because it is more efficient than
                                                      crushing to a relatively small size in a single-
    1. All vegetation is removed over the dump        stage operation. First stage, or primary, crush-
area.                                                 ers are usually jaw crushers in small operations
    2. The surface of t h e dump area is              and gyratory types in larger operations. Pri-
compacted and overlain by impervious                  mary crushers and the coarse ore bins may be
material such as clay.                                located at the mine, where the mine and mill
    3. Fine material should be separated.             operation are separated. Secondary crushers
    4. A long, narrow dump may be desired to          and the fine ore bins are usually at the mill,
promote natural aeration.                             along with blending or custom facilities where
    5. The surface of the dump is ripped, or other-   more than one kind of ore is mined or received.
wise uncompacted.                                     The fine ore is ground in ball or rod mills to a
    6. The dump material may be moistened as it       size small enough to liberate the ore minerals,
is laid down, inducing oxidation while the            then classified in various kinds of machines to
material is s t i l l i n direct contact w i t h      insure that the feed to the mill is uniform.
atmospheric air.                                         The various ore dressing methods are based
   7. The dump may be leached in a series of          on physical characteristics such as density,
"lifts," which has been found to be more              wettabil ity, chemical reactivity toward certain
efficient than attempting t o leach the entire        reagents, and magnetic characteristics.
waste dump in a single operation.                        Flotation.--Flotation is the most widely used
   Heap Leaching.--Heap leaching is applied t o       method of beneficiating complex and low-
ores where the grade is too low to pay for            grade sulfide ores in the western United States.
haulage, conventional concentration, o r              The word "concentrator" is virtually synony-
leaching in a vat operation. Complex ores that        mous with froth flotation plant. The crushed,
ground, and classified ore is pulped with water,     some deposits this means simple screening of
and special reagents are used to make one or         the material as it comes from the mine, break-
more of the ore minerals water repellent and         ing oversize to 6 inches or more. Low-grade
responsive to attachment with air bubbles. As        barite ores have been economically upgraded
the desired minerals are buoyed to the surface       using the sink-float process, and the method
by the attached air bubbles, they are removed        has found application in upgrading coal.
by mechanical paddles as concentrate, leaving           Magnetic Separation.--Approximately 20
the other minerals behind. Often several             ores are magnetic enough to be separated by
stages of flotation with selective reagents are      the magnetic process. The separation can be
employed to obtain the desired concentration.        either wet or dry. In one wet process, magnetic
   Pneumatic, or air, flotation cells are long,      drum separators are used to lift the magnetic
open troughs through which the pulp flows,           particles from a stream of ore pulped with
and gas bubbles are introduced from the bot-         water. In a typical dry process, the magnetic
tom to accomplish agitation and frothing.            particles are lifted from the moving stream of
Mechanical cells are boxlike and are agitated        ore by a fast moving magnetic cross belt.
by a rotating impeller through which air bub-
bles are introduced.                                         Extractive Metallurgy
   Gravity.--Gravity methods of concentration           Extractive metallurgy involves the recovery
are based on the simple fact that the ore min-       of metals and metal compounds from ores and
erals are heavier than the gangue. Gravity may       mineral concentrates. Pyrometallurgy, hydro-
be the sole method of concentration, or the          metallurgy, and electrometallurgy are t he prin-
equipment may be a part of the mill "flow"           cipal methods involved. As these names imply,
scheme, where waste material is separated in         heat, aqueous solutions, and electric current
a series of steps. The jig is a boxlike apparatus
                                                     are used to produce metals and metallic com-
containing a submerged screen that supports          pounds of sufficient purity for the market.
a bed of ground ore. The ore is stratified by the
action of two pulses of water, one upward,              Pyrometal1urgy.--Electrical energy is used
downward, alternating in rapid succession.           or fuels are burned to apply sufficient heat in
During this pulsation, particles of different        refractory-lined furnaces to melt the charge of
density arrange themselves according to size         ore or mineral concentrate in the pyro-
and specific gravity, the tailing forming the        metallurgical process. Some minerals are
                                                     volatilized at elevated temperatures and can be
top layer, a fine concentrate passing through
                                                     recovered by distillation from kilns, furnaces,
the screen, and a coarse concentrate forming
                                                     and retorts. Other metals can be separated by
in a layer on the screen.
                                                     liquation, using differences in melting point.
   Shaking tables are inclined, elongated decks         Smelting is by far the most important of
with cleats nailed to the surface. The table is      the pyrometallurgical processes. The ore and
vibrated lengthwise with a slow motion in one        waste minerals are heated, altered, fluxed, or
direction and a rapid return. A thin layer of        reduced to form a low-density slag and one or
water flows down and over the deck, and slurry       more liquid metals. Only high-grade ores or
feed is introduced at the upper corner. Small,       concentrates can be smelted because of the
heavy particles ride high on the table, parallel     high cost. It is usually necessary to further re-
to the cleats, to the end where they are col-        fine the metal to a product of acceptable purity.
lected. Light material washes over the cleats,          All pyrometallurgical operations produce
down to the lower side where it spills over into a   large volumes of gas containing a wide variety
trough and is directed toward the tailings dis-      of vaporized metals, dust, and fumes. Many
posal area.                                          smelters are large centralized installations that
   Where heavy, insoluble minerals are involv-       have gradually evolved over the years at some
ed, a liquid of specific gravity intermed-           major seaport, rail point, or other shipping
iate between ore and waste can be used to            center. Only in a rare situation would a smelter
make the separation in the process called sink-      be planned near a single mining operation in a
float. The ore need be broken only fine enough       region with relatively poor transportation
to separate ore minerals from waste, and in          facilities.
   Hydrometa1lurgy.--Hydrometal lurgical pro-
 cesses selectively dissolve metals from ores
 and concentrates, resulting in recovery of             In mountainous terrain, particularly where
 relatively pure metal. Various acids, such as       development is by adit and where access is dif-
 sulfuric acid, and alkaline solvents, such as the   ficult, waste dumps are located in or near the
 hydroxides and carbonates of sodium or              stream bottoms. Normally, waste is dumped
 ammonium, are popular in leaching ores.             just beneath the level of the adit portal or shaft
Sodium and calcium cyanide solutions are             collar.
widely used in extracting gold and silver from          Where a reservoir may be desired as a source
precious metal ores.                                 of water for mine, mill, and townsite, it may
   The usual technique is to agitate finely          be possible to locate the mine waste dump so
ground ore or concentrate in open vessels at         as t o impound water. Many such reservoirs
atmospheric pressure. Vat leaching percolates        have become important recreational assets for
crushed ore bedded in large, stationary, rec-        employees and the public.
tangular, or circular containers. There is              There is no general fixed ratio for the amount
presently much interest in these processes,          of waste produced compared to ore, but in
because many ores that were formerly smelted          most cases it is less than 1:1 waste:ore i n
may be treated by hydrometallurgy with far           underground mining operations. At certain
less air pollution and consumption of energy.        points in the development of bulk mining op-
   Electrometallurgy.--Two kinds of electro-         erations, such as block caving, for brief
metallurgical processes are in general use to-       periods virtually all of the material taken from
day. In one, the electric current is used as a       the mine will be waste rock. Shafts for ore haul-
source of heat; in the other, the current is used    age systems may deliberately be laid out well
in electrolytic depositon on cathodes. Electri-      away from the ore body in waste rock to insure
cal heating is substituted for fuel heating          that these facilities will not be damaged or
where precise control of temperature is re-          destroyed by mining.
quired, or the atmosphere of the furnace or             Open pit operations, such as phosphate and
purity of the metal is of concern.                   copper, produce far more waste rock than
   Electrolytic processes include two general        underground methods, and disposal of this
methods, one using an aqueous electrolyte,           material is a major aspect of the operation. It
the other a fused salt electrolyte maintained        is common for the ratio of waste to ore to
at high temperature. The aqueous electro-            exceed 1:1, and in some cases 10 tons or more
lyte method is widely used to purify metal           of waste are removed for each ton of ore taken
produced by pyrometallurgical methods.               from the pit.
                                                        In the large view, some planners see major
                                                     open pit mines as a solution t o the surface
                                                     disturbance problem. They are efficient and
                                                     highly productive of metal, concentrating dis-
                                                     ruption in one local area rather than having the
                                                     same production come from tens or hundreds
   Some high-grade ore deposits are so mas-          of smaller operations scattered through the
sive and so easily distinguished from wall           region. For example, in Nevada, one small
rock that they can be removed by highly se-          cluster of open pit copper mines, embracing
lective mining methods underground. A mod-           an area of several square miles, has produced
erate amount of waste rock produced during           more copper and molybdenum than all of the
development of haulageways through barren            other mines in the State combined, by a very
wall rock can often be disposed of as stope fill     wide margin.
with the result that there are no large waste          As in other kinds of surface reclamation, it is
dumps at the surface. More often, a consider-        usually much more economic to plan the best
able amount of barren or low-grade material is       waste disposal before the material is placed.
taken from the mine during exploration and           Satisfactory solutions can often be worked out
development, and disposal of broken waste            beforehand at an acceptable increase in
rock on the surface is a major problem.              operating cost, particularly where the solution
can be coordinated with other phases of the        treat mine water by various processes before
operation, such as providing a superior yard       releasing it, as for example neutralization of
facility for the machine shops or better layout    acid by using lime or caustic soda. Mine water
of a mine dump leaching operation.                 may be used directly in the mill boilers, where
  There is a certain amount of noise pollution     it may be recycled to further reduce contam-
in drilling, blasting, movement of large equip-    ination of surface water.
ment, and the operation of air compressors,           Some mine water is of sufficiently good
powerplants, crushers, and mil Is. This noise      quality to become an important local source
usually affects only the people in the im-         and environmental asset.
mediate area of the mine and mill, who are
employees of the operation. Most mine opera-
tors are attempting to reduce noise wherever
                                                                  Mill Wastes
possible, in line with recent industrial safety       Because most mill wastes are finely ground
studies, which show that worker fatigue can        and are moved to disposal areas in a water
result from noisy environments.                    slurry, particular problems are encountered
                                                   with the environment. In many milling opera-
   The water draining from newly opened or
                                                   tions the ore constitutes only asmall portion of
abandoned mines can have a major impact up-
                                                   the material recovered as concentrate. For
on the environment downstream. Solid partic-
                                                   example, only 2 or 3 percent of the weight of
ulate matter may be introduced in sizes rang-
                                                   ore in a low-grade copper mine ends up as con-
ing from fine silt to sand, and consisting of
                                                   centrate. The 97 to 98 percent waste must be
relatively inert material, although chemical re-
                                                   disposed of as mill tailings, which are directed
actions may convert some or all of it to more
                                                   through ditches, launders, and pipesystemsto
soluble chemical compounds. Radioactive
                                                   pond disposal areas downhill from the mill. In
material may be involved in some cases, and
                                                   some cases, mill tailings can be classified and
organics may be introduced into surface
                                                   returned underground to be nozzled under
waters. Mine waters are often "acid" because
                                                   pressure as stope fill.
of the common association of the iron sulphide
                                                      Mill tailing ponds are usually impounded
pyrite with most metal ores and many solid
                                                   behind embankments built from the tailing
fuels. Pyrite, as well as a number of other ore
                                                   material itself. Sometimes it is necessary to in-
and gangue minerals, rapidly decomposes
                                                   stall drainage systems beneath the dam and
when broken and in contact with moisture and
                                                   pond area to facilitate drainage where the
air, producing sulphuric acid. This chemical
                                                   natural ground is not sufficiently porous. The
reaction proceeds spontaneously, and the acid
                                                   site should be selected so that surface water
mine water then has the ability to take other
                                                   cannot erode the toe of the embankment. It is
pollutants into solution.
                                                   usually necessary to construct a catchment
   Mines where broken or ground pyritic            pond downstream from the embankment to
material has been used as stope fill are par-      collect seepage water and tailings eroded from
ticularly likely to produce acid water; it is      the face of the embankment. Decant systems
possible to minimize this to some extent by        take off the water after solids have separated,
shutting off this portion of the mine, or other-   and the floor of the pond gradually rises as
wise keeping the supply of oxygen and mois-        disposal continues. A major threat to the tail-
ture from these areas. Alternatively, a mine can   ings pond is overflow of the embankment due
be partially or entirely flooded with water to     to flooding in the drainage system above the
eliminate oxygen.                                  tailings. Abandoned, poorly designed tailings
   When it becomes necessary to reopen old         ponds are quite troublesome in this regard,
mines, they are often found to be partially        particularly where no attempt was made to
flooded with acid water containing much dis-       stabilize the surface, or to divert surface water
solved material. It may be possible to gradually   away from the area.
release such water into surface drainage              When the surface of an unstabilized tailings
during the runoff season. Sudden release           pond is allowed to dry, major pollution of the
during low water would cause major environ-        nearby area can occur when fine particles are
mental damage. It is sometimes possible to         picked up by the wind. Proper location, design,
and operation of the disposal system mini-            boundary, and a gatekeeper may allow entry
mizes some of the difficulties. Again, old aban-      only to company employees or people having
doned tailings are often a major problem.             legitimate business on the property. There are
  Dissolved metals and salts, in highly toxic         a number of reasons why mining companies do
solutions, are sometimes found leaching from          not permit people to enter the property at will.
mill tailings. Modern practice is to remove this      An unsuspecting tourist could easily drive off
material where it is at all feasible to do so.        an open pit bench, fall into a tank full of so-
                                                      lution, or become involved in any one of a hun-
          Miscellaneous Junk                          dred other industrial hazard situations. Expo-
                                                      sure to public liability alone is enough to make
    In many of the old mining camps of the West,
                                                      most companies enclose the mine and mill
 every trace of former mining activity has been
                                                      area in chain link fence.
 removed by scavengers to the point that the ex-
 act position of some small districts of historical      Many companies recognize the damage to
 record can no longer be found with certainty.        their public image when the typical curious
 In some areas of more recent activity, for ex-       tourist may suddenly be confronted with acurt
 ample the gold mines of the 1930's and tung-         rebuff at the end of a well-traveled and main-
sten mines of the 19501s,the mine buildings           tained road, and thought is usually given to
 and equipment are less romantic, gradually           minimizing the effect. Most open pit operators
 having fallen into a state of vandalized disre-      arrange guided tours or self-guided Vantage
 pair that in every way qualifies them as the         points where the visitor can gain a clear per-
 prime local eyesore. Eventually, all of the iron     ception of the mine operation, yet stay at adis-
will be taken for scrap, the tanks appropriated       tance where he will not be in the way or ex-
by local ranchers and farmers, and the wood           posed to any risk. Mine tours and viewpoints
and galvanized sheeting hauled away. In the           engender a great amount of good will for the
meantime, there is often little that can be done      mining industry, and go a long way toward
to quickly clean up these areas, unless some          eliminating a potential source of friction be-
local regulation permits them to be classified        tween mine operator and the public.
as esthetic nuisances or safety hazards.                 Many mine operators recognize that facili-
   If a considerable amount of junk has been          ties such as reservoirs, or the drainage system
left in a district or group of districts, it may be   behind them, that provide water for mine, mill,
possible to arrange for outside scrap collectors      and townsite have a considerable recreational
to make contact with the owners for a bid             potential for employees. Because local fish
on salvage. Caution should be exercised, how-         and game authorities will not usually stock or
ever, for these old facilities sometimes are clas-    manage game on private lands from which the
sified as genuine antiquities at about 50 years       public has been excluded, and because of prob-
of age, and public sentiment may be very much         able adverse public opinion if the areas are
divided as to the merit of removal.                   restricted to employee use, such recreational
   In presently operating mines, or newly plan-       areas are often opened to the public, with the
ned operations, it is possible to insure removal      normal restrictions of a private landowner.
of the surface plant and equipment. There are         More than the usual number of signs caution-
problems, however, with the law insofar as the        ing potentially hazardous situations are post-
rights to structures on lands optioned or leased      ed, because of the private landowner's expo-
from private individuals that may for one rea-        sure to possible liability. Companies have been
son or another revert to original ownership.          known to subsidize or entirely finance boat
                                                      landings, beaches, parks, camping facilities,
                                                      and ski lifts and lodges, and have been involved
                                                      in game management programs, such as
                   Roads                              stocking of fish and reintroduction of game
  In most cases, where public funds are used          animals, where such projects would not be
for road construction and maintenance, the            economically sound for a private individual.
public may have some use of the roads. This             The public is allowed use of mine access
may abruptly terminate at the mine property           roads to recreational areas. There are some-
times unusual traffic controls, rights-of-way,     where the driver might experience difficulty if
and traffic movement patterns. One-way traffic     he were to suddenly lose control. This results
may be necessary at certain times on narrow        in a considerable amount of travel on the left
roads where large off-highway units are used.      side of open pit haul roads.
Water trucks may dissipate dust almost con-          When a road has been constructed by the
tinuously to improve driving safety and to re-     Forest Service for Forest purposes, the miner
duce wear on truck bearings and engines. On        who desires to use it may be required to share
unsurfaced haulage roads where large trucks        the cost of maintenance, based perhaps upon a
are used, the traffic flow is often directed so    ton per mile fee for the miner's proportional
that loaded trucks are against the hill rather     use of the road. The miner may be required to
than out on the bank, where the weight of the      maintain or help to maintain such a road in the
load may break the edge of the road down, and      condition it was originally designed for.




I   RECLAMATION




   There is a widespread public feeling that the   quire land reclamation as an integral part of
mining industry has defaced vast areas; this       mine planning. A large percentage of mined
belief probably in part originates because         land is now being reclaimed, or at least par-
roads and other transportation facilities are      tially reclaimed to an acceptable condition.
well-developed in established mining areas.           Extensive research is being conducted by
The area affected by mining is about a sixth       mining companies, several Government agen-
that devoted to highways, and is approximately     cies, including the Forest Service through its
equal to that used for airports in this country.   SEAM program, and university scientists on
In terms of benefit to the Nation, mining is es-   the many technical facets of reclamation. Re-
sential and in all fairness modern, well-planned   sults are being shown at demonstration areas,
and operated mines are not the despoilers          and are being rapidly incorpoated into mine
many believe them to be.                           planning and continuing operations.
   Over the years, the increased size and ef-         This brief chapter makes no attempt to dis-
ficiency of powered excavation equipment and       cuss the many technical facets of reclamation.
improved drilling and blasting techniques have     Rat her, it briefly presents several general
resulted in very low cost mining operations. As    concepts.
the individual and total number of these bulk         Satisfactory reclamation should emphasize
mining operations have grown, so has public        three major objectives:
interest in reclamation of the surface disturb-       1. The productivity of the reclaimed land
ance resulting from them. Many States now re-      should at least equal that of the premine sur-
face. This does not necessarily mean that the       wastes and to restore the surface t o anything
site must be restored to an approximation of its    like the original contour. Planning must take
original condition, or that surface uses after      the reality of the situation into account and aim
mining will be the same as those existing prior     toward possible ultimate benefit to be derived
to mining. For example, an area used for mar-       from a surface configuration much different
ginal grazing prior to mining may be changed        than prior to mining.
to a useful and attractive recreational complex,
                                                      There are no cut and dried standard formu-
or perhaps in another case to a housing area.
                                                    las for accomplishing reclamation. Almost
   2. Satisfactory reclamation should leave the
                                                    every case differs and is influenced not only by
mined area in a condition that will not contri-
                                                    natural variables such as climate and the ma-
bute to environmental degradation either in the     terial to be worked with, but by social variables
form of air- or water-borne materials, or from      such as the laws of the particular State where
chemical pollution.                                 the operation is located, the ownership of the
   3. The reclaimed area should be esthetically     land, and the goals the public may wish to see
acceptable and it should be safe for the uses       pursued through reclamation. In addition, the
intended.                                           operator's requirements as to methods of min-
   Reclamation goals must not only be techni-       ing and timing will affect the final decision con-
cally feasible, they must be economically at-       cerning specific prescriptions for reclamation.
tainable. In some cases restoration to the ori-
ginal contour is not practical. For example, in a      Mining companies now generally have ex-
major open pit copper operation, 500 million        pertise available for planning reclamation.
tons of ore are mined and sent to the mill, and a   Land managers can be of assistance by partici-
billion tons or more of overburden will be pla-     pating in the planning process and by contrib-
ced on waste dumps. Milling will result in al-      uting technical knowledge where possible
most 500 million tons of tailings, and 10 to 15     and where needed. Assistance often can be
million tons of concentrate that will be shipped    given on specific information such as plant and
to the smelter, and from which 5 million tons of    wildlife species, seeding methods, labor sourc-
copper metal will be recovered. The excavation      es, and plant material sources. The final de-
of a billion and a half tons will leave a hole      cisions on reclamation will most often be the
nearly a cubic mile in size. Using presently        result of the combined contributions from
available mining methods, particularly at           many sources, both public and private. Rec-
mines already partially developed, it is not pos-   lamation ideally is just another end result of
sible to economically replace the mine and mill     thorough mine planning.
U.S. Department of Agriculture, Forest Service. 1995. Anatomy of a mine from prospect to
  production. Gen. Tech. Rep. INT-GTR-35 revised. Ogden, UT: U.S. Department of
  Agriculture, Forest Service, Intermountain Research Staion. 69 p.
  Reviews mining laws and regulations and their application to mining in Western States.
Describes prospecting, exploration, mine development and operation, and reclamation
factors.


Keywords: mining law, mineral exploration, mine development, mine operation, mining area
          reclamation




              Federal Recycling Program   p
                                          c     Printed on Recycled Paper
                                                                    INTERMOUNTAIN
                                                                   RESEARCH STATION




   The lntermountain Research Station provides scientific knowledge and technology to improve manage-
ment, protection, and use of the forests and rangelands of the lntermountain West. Research is designed to
meet the needs of National Forest managers, Federal and State agencies, industry, academic institutions,
public and private organizations, and individuals. Results of research are made available through publica-
tions, symposia, workshops, training sessions, and personal contacts.
   The lntermountain Research Station territory includes Montana, Idaho, Utah, Nevada, and western
Wyoming. Eighty-fivepercent of the lands in the Station area, about 231 million acres, are classified as forest
or rangeland. They include grasslands, deserts, shrublands, alpine areas, and forests. They provide fiber for
forest industries, minerals and fossil fuels for energy and industrial development, water for domestic and
industrial consumption, forage for livestock and wildlife, and recreation opportunities for millions of visitors.
   Several Station units conduct research in additional western States, or have missions that are national or
international in scope.
   Station laboratories are located in:

  Boise, ldaho

  Bozeman, Montana (in cooperation with Montana State University)

  Logan, Utah (in cooperation with Utah State University)

  Missoula, Montana (in cooperation with the University of Montana)

  Moscow, ldaho (in cooperation with the University of Idaho)

  Ogden, Utah

  Provo, Utah (in cooperation with Brigham Young University)

  Reno, Nevada (in cooperation with the University of Nevada)

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of race, color, national origin, sex, religion, age, disability, political beliefs, and marital or familial status. (Not
all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for
communication of program information (braille, large print, audiotape, etc.) should contact the USDA's
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   To file a complaint, write the Secretary of Agriculture, U.S. Department of Agriculture, Washington, DC
20250, or call 1-800-245-6340 (voice) or 202 720-1127 (TDD). USDA is an equal employment opportunity
employer.

								
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