This file was created by scanning the printed publication. Errors identified by the software have been corrected; however, some errors may remain. 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. 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