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                                                                    RARE EARTH ELEMENTS


Potential and Outlook                                      in the Earth’s crust than silver, gold or platinum, while
                                                           cerium, yttrium, neodymium and lanthanum are more
New South Wales has excellent potential for                common than lead.
commercial deposits of rare earth elements, principally
                                                           The elemental forms of REE are iron-grey to silvery
in trachyte intrusions of Mesozoic age. The Toongi
                                                           lustrous metals (Harben 1999). Typically, they are soft,
prospect (Toongi) (Figure 22), which is one of
                                                           malleable and ductile, and usually reactive (rapidly
numerous intrusions in the central west of New South
                                                           forming rare earth oxides), especially at higher
Wales, is a potentially world-class source of rare earth
                                                           temperatures or when finely disseminated. REE are
elements. This intrusion is about 24 km south of
                                                           never found as free metals in rocks. They typically
Dubbo and consists of hydrothermally altered alkali
                                                           occur as mixtures of various REE-bearing minerals
trachyte with anomalous rare metal and rare earth
                                                           and require mineral separation from each other for
elements, principally zirconium oxide, niobium/
                                                           commercial use.
tantalum oxide and yttrium oxide.
                                                           Bastnaesite, (Ce,La)(CO3)(OH,F); xenotime, YPO4; and
Beach placers along much of the coast north of Sydney
have heavy mineral assemblages that are dominated          monazite, (Ce,La,Nd,Th)PO4.SiO4 are the three most
by rutile and zircon, and minor amounts of monazite.       economically significant minerals of the more than
These deposits are largely depleted, uneconomic or not     200 minerals known to contain essential or significant
accessible. The rare earth potential of heavy minerals     REE (Christie et al. 1998). Bastnaesite and monazite
sands deposits in the Murray Basin, which have small       are sources of light REE and account for 95% of REE
proportions of monazite and xenotime, has yet to be        currently used (Harben & Kuzvart 1996). Xenotime
fully assessed.                                            is a source of the heavier REE and yttrium. Monazite
                                                           is also the principal ore of thorium, containing up to
                                                           30% thorium. Together with small amounts (up to
                                                           about 1%) of uranium, thorium imparts radioactive
Nature and Occurrence                                      properties to the monazite.
The rare earth elements (REE) are the 15 lanthanide
                                                           In 2004, global production of rare earths was about
elements with atomic numbers 57 to 71 (Christie
                                                           102 000 tonnes, mainly from bastnaesite and monazite
et al. 1998). In order of increasing atomic number,
                                                           deposits, some 90 000 tonnes of which came from
they are lanthanum (La), cerium (Ce), praseodymium
                                                           China (Hedrick 2005). Other producers of REE
(Pr), neodymium (Nd), promethium (Pm), samarium
                                                           included Russia, India, Malaysia and Sri Lanka. Global
(Sm), europium (Eu), gadolinium (Gd), terbium (Tb),
                                                           resources of rare earths are estimated at 88 million
dysprosium (Dy), holmium (Ho), erbium (Er), thulium
                                                           tonnes (about one third held by China), primarily in
(Tm), ytterbium (Yb) and lutetium (Lu). Yttrium (Y),
                                                           bastnaesite and monazite. Hedrick (2005) concluded
scandium (Sc) and thorium (Th) are generally included
                                                           world rare earth resources are very large compared to
with the REE as they occur with them in minerals and
                                                           their expected demand.
have similar chemical properties.
REE are classified into two groups: light REE or cerium
group (lanthanum to europium) and the heavy REE,           Deposit Types
comprising gadolinium through lutetium, as well            REE minerals occur in a diverse range of igneous,
as yttrium and scandium. The light REE are more            sedimentary and metamorphic rocks (Sawka et al.
abundant than the heavy REE.                               1990; Harben & Kuzvart 1996; Jones et al. 1996;
                                                           Christie et al. 1998). Their principal geological
The term ‘rare earths’ was proposed in 1794 (Christie
                                                           environments are summarised below.
et al. 1998). The term ‘rare’ was used because when
they were found they were thought to be present in         1. Carbonatites: carbonate-rich rocks of magmatic
the Earth’s crust in only small amounts, and ‘earths’         origin are commonly associated with major faults,
because as oxides they have an earthy appearance.             lineaments and explosive volcanism. Typically
Despite their name, the REE are each more common              the last magmatic stage in alkaline–carbonate
                                                                   150°00’E                                                                  TWEED HEADS          155°00’E




                                                                                                                                             BYRON BAY




                                                                                                             TENTERFIELD
                                                                                                                                                                     N

                         LIGHTNING RIDGE
                                                                     MOREE



                                                                                      INVERELL
                                                                                                                      GRAFTON                      0                               100
 30°00’S
                                                                                                                                                                 kilometres

                                                                                                                                                                                      30°00’S

                                                                 NARRABRI
                                                                                                                                 COFFS HARBOUR
                                                                                                  ARMIDALE



                                                                                                                                        REFERENCE

                                                                               TAMWORTH
                                                                                                                                        Rare earth occurrence - monazite

                                                                                                                                        Rare earth occurrence - excluding monazite


           NYNGAN
                                                                                                                            PORT MACQUARIE
                             GILGANDRA

                                                                                                                                                             STUDY
                                                                                                                                                             AREA

                                                                              SCONE

                                         DUBBO


                                         Toongi deposit
                                                          MUDGEE



                                                                                                                                                            NT
                                                                                                  NEWCASTLE                                                          Qld
                                                                                                                                                  WA
                    PARKES
                                                                                                                                                            SA
                                                                                                                                                                         NSW
                                                 ORANGE
                                                     BATHURST                                                                                                        Vic.

                                                                                                                                                                            Tas.

                                                                150°00’E                                                                         155°00’E
                                                                                                                                                                                   2005_05_0109




     Figure 22. Rare earth element occurrences in New South Wales, excluding mineral sands




   complexes (e.g. syenites, nepheline syenites and                                              and loparite, (Ln,Na,Ca)(Ti,Nb)O3, form as
   nephelinites). Bastnaesite-bearing carbonatite is                                             magmatic deposits in the host igneous rocks, and
   the world’s main source of REE. Examples of REE-                                              as metasomatic deposits in veins, stockworks and
   bearing carbonatite deposits include Bayan Obo in                                             irregular replacement zones. Examples include the
   Inner Mongolia, China; Mountain Pass, California;                                             Kola Peninsula, Russia; and the Brockman deposit,
   and the Mineral Hill district, Idaho–Montana.                                                 Western Australia.
2. Beach placers containing detrital REE minerals                                        4. Iron–REE deposits, perhaps the largest being the
   of high specific gravity, principally monazite and                                       Olympic Dam (South Australia) hematitic granite
   xenotime. These minerals are extracted from beach                                        breccia-style (IOCG) deposit. This is a very large
   placers that are mined primarily for their rutile,                                       deposit, in the order of several thousand million
   zircon and ilmenite contents. Examples include                                           tonnes, that consists of disseminated chalcopyrite,
   eastern and western Australia; Florida and Georgia                                       bornite and chalcocite accompanied by gold,
   in the USA; South Africa; India; and Sri Lanka.                                          uranium, silver, barium, REE and fluorine minerals
3. Peralkaline syenitic and granitic igneous rocks are                                      (Christie et al. 1998). Extremely fine-grained
   characterised by the occurrence of alkali amphibole                                      monazite and bastnaesite are the most common
   and pyroxene minerals. REE minerals, principally                                         REE minerals at Olympic Dam, which contains
   eudialyte, Na(Ca,La)2(Fe,Mn,Y)ZrSi8O22(OH,Cl)2,                                          0.2% La and 0.3% Ce.
5. Pegmatites, hydrothermal quartz and fluorite veins        hosted by hydrothermally altered trachyte. The deposit
   of various origins. Examples include Northern             contains a resource of 50 million tonnes at 4400 ppm
   Territory, Australia (pegmatites); Karonge, Burundi       Nb2O5, 270 ppm Ta2O5, 1240 ppm Y2O3, 110 ppm Ga,
   (hydrothermal quartz); and Naboomspruit, South            350 ppm HfO2, 900 ppm REE and 1.03% ZrO2 (Aztec
   Africa (fluorite veins).                                  Resources Limited 2005).
6. Skarn deposits (not associated with carbonatites),
   which include the Mary Kathleen U–REE–Th
   skarn, Queensland (now mined out). This deposit           New South Wales Occurrences
   contained REE minerals hosted in uraninite, apatite       In the central western part of New South Wales,
   and allanite developed in garnet-bearing calcsilicate     mainly north of Rylstone (near Mudgee) and south of
   rocks near an alkali granite intrusion.                   Dubbo (Figure 22), there are numerous Mesozoic sills,
7. Residual laterites enriched in REE that formed by         laccoliths, dykes and flows (Warren et al. 1999). They
   intense subtropical weathering of REE-rich alkaline       range in composition from basalt to alkali diorite to
   complexes. These deposits occur predominantly as          trachyte, syenite and phonolite. The intrusions appear
   mineral assemblages of goethite, hematite, aluminium      structurally controlled and are aligned along large-
   hydroxides, kaolinite minerals and quartz, and            scale lineament sets. In New South Wales, trachyte
   typically contain 10% to 25% rare earth oxides (REO).     intrusions appear to have the greatest potential for
8. Residual deposits of REE-bearing clays, termed ionic      commercial occurrences of REE.
   or ion-adsorption type ores, develop in association       The Toongi prospect (Toongi), which is about 24 km
   with weathered granites. Ion-adsorption ores              south of Dubbo (Figure 22), is a small, altered
   are only known from China (Long Nan, Yianxi,              alkali trachyte intrusion of Triassic age containing
   southern China). Rare earth cations released during       anomalous rare metal and rare earth elements
   weathering of granites were adsorbed by kaolin and        (Chalmers 1999; Alkane Exploration Ltd 2004).
   various aluminosilicates. They have grades of about       Hydrothermal alteration involving significant
   1% REO and are characterised by very low cerium           carbonate, chloritic, potassic and argillic alteration has
   content and a rare earth content that is rich in          modified the Toongi prospect (Downes 1999). The REE
   samarium, europium and terbium, or yttrium.               mineral assemblage is very fine-grained and includes
                                                             bastnaesite, zirconium silicate, yttrium silicates and
                                                             niobium–tantalum silicates.
Main Australian Deposits                                     Toongi, also known as the Dubbo Zirconia Project, has
Australia was formerly the world’s largest producer of       resources of 73.2 Mt @ 1.96% ZrO2, 0.04% HfO2, 0.46%
monazite, almost entirely from beach placer deposits         Nb2O5, 0.03% Ta2O5, 0.14% Y2O3 and 0.745% total REO
in New South Wales, Queensland and Western                   (Alkane Exploration Ltd 2004). Feasibility studies
Australia (Harben & Kužvart 1996). There has been            envisage production of 200 000 tonnes per annum of
no commercial production of monazite from those              ore to produce 3000 tonnes of zirconium, 600 tonnes
sources since 1995 (ABARE 2001). There are several           of niobium and tantalum and 1200 tonnes of yttrium–
deposits in Western Australia, the Mount Weld deposit        rare earth products.
and Brockman deposit (see following discussion).
                                                             Lateritic nickel, cobalt and scandium resources have
Production has yet to begin at either deposit (late 2005).
                                                             been identified at Lake Innes, near Port Macquarie
Mount Weld, Western Australia, is a major REE                (Figure 22) (Douglas McKenna & Partners Pty Ltd
deposit that is developed in laterites formed on             2003). Serpentinite complexes occur in a Permian fault
a carbonatite diatreme of Palaeoproterozoic age              zone in Silurian–Devonian rocks. Locally, over the
(Fetherston 2002). REO contents up to 40% have been          serpentinite complexes, laterites, containing weathered
found in the laterites. Mount Weld has resources             serpentinite, saprolite, limonitic clay and hematite
of 7.7 Mt at a grade of 11.9% rare earth oxides,             clay, range in thickness from 10 m to 30 m. Scandium
which represents about 917 000 tonnes of rare earth          tends to occur in the upper part of the lateritic profile,
oxides (Lynas Corporation Ltd 2002, 2003). Mining            whereas cobalt and nickel are found in the middle
operations began in mid 2007.                                and lower parts of the profile. The deposits contain
The Brockman deposit, Western Australia, is a                15.7 million tonnes of nickel at 1.46% nickel, 0.09%
potential source of tantalum–niobium and heavy REE           cobalt and 41 ppm scandium.
(Castor 1994). The REE occur as very fine-grained            Alkali pyroxenite rocks from the Staurolite Ridge
minerals disseminated in metamorphosed rhyolitic tuff        intrusion, Broken Hill, contain altered ultrabasic
rocks with high (about 35%) granoblastic carbonate          in applications such as cigarette lighters, miners’ safety
(Barron 1978). The potential in New South Wales             lamps and automatic gas-lighting devices.
for carbonatite-hosted REE minerals, however, is
                                                            Scandium is used mainly as a component of
unknown. There may be some potential for REE
                                                            aluminium alloys in baseball and softball bats; as
deposits in A-type granites, and also A-type volcanic
                                                            alloys, compounds and metals in metallurgical
rocks (L.M. Barron pers. comm., 2004). A-type
                                                            research; sporting goods equipment; semi-
granites are highly evolved granites in which fluids
                                                            conductors; and speciality lighting (Hedrick 2005).
enriched in REE, elements such as Nb, Ta, Zr, Hf, Th, U
                                                            Overall, scandium consumption is very small.
and Y, and volatiles such as F, P and CO2, accumulated
                                                            Yttrium is primarily used in lamp and cathode
late during their formation (Sawka et al. 1990). In New
                                                            phosphors and lesser amounts in structural
South Wales, A-type granites are associated with the
Bega Batholith and Wyangala Batholith, and A-type           ceramics and oxygen sensors.
volcanic rocks with the Comerong and Boyd volcanic
complexes (Chappell et al. 1991).
                                                            Economic Factors
                                                            Several very large deposits, including Mianing in
Applications                                                China, the Mount Weld deposit in Western Australia
Rare earths have numerous, diverse, highly specialised      and the Dubbo Zirconia Project, have yet to be
applications (Christie et al. 1998; Hedrick 2005). The      fully developed. Long-term demand for monazite is
largest use of rare earth oxides is in mixed forms,         expected to increase because of its abundant supply
principally in petroleum fluid-cracking catalysts and in    and its recovery as a low-cost by-product of mineral
rare-earth phosphors for television, X-ray intensifying,    sands mining.
and fluorescent and incandescent lighting. These forms      There is an expanding market for rare earths. Their
are listed below.                                           use in automobile pollution catalysts, permanent
•	 Globally, about 35% of REE are used as catalysts,        magnets and rechargeable batteries, should increase
    mainly in the refining of crude oil to improve          (Hedrick 2005). Strong demand for cerium and
    cracking efficiencies and in automobiles to improve     neodymium for use in automobile catalytic converters
    oxidation of pollutants.                                and permanent magnets is expected to continue over
•	 Some 30% of REE are used in the glass and                the next five to ten years. Future demand is likely for
    ceramics industry as glass-polishing compounds,         rare earths in rechargeable batteries, fibre optics and
    decolourising agents, UV absorbers, colouring           various medical applications. Long-term growth is
    agents, in optical lenses and glasses, and additives    expected for rare earths in magnetic alloys for such
    to structural ceramics — such as stabilised zirconia    uses as electric generators and air conditioners.
    and silicon nitride.
•	 About 30% of REE are used in metallurgy as
    an alloying agent to desulphurise steels, as a          References
    nodularising agent in ductile iron and as lighter       ABARE 2001. Australian commodity statistics 2001.
    flints. REE are also used as alloying agents            Australian Bureau of Agricultural and Resource Economics
    to improve the properties of superalloys and            (ABARE), Canberra.
    magnesium, aluminium and titanium alloys.               Alkane Exploration Ltd 2004. Annual Report 2004.
Other uses of REE include lasers, microwave applications,   www.alkane.com.au
alloys, computer memory and specialised ceramics
                                                            Aztec Resources Limited 2005. Latest News.
(Harben & Kužvart 1996). Rare earths enable glass fibres    www.aztecresources.com.au
to transmit information over long distances without
booster stations. Samarium–cobalt batteries have largely    Barron B.J. 1978. Unpublished petrological report No.
replaced more expensive platinum–cobalt batteries.          78/22: petrographic features of alkali pyroxenite rocks
                                                            from the Staurolite Ridge intrusion Broken Hill N.S.W.
Mischmetal, an alloy composed of Ce, La, Nd, Pr, Sm,        (in conjunction with mapping of the Pinnacles sheet by
Tb and Y and iron, about 5%, is a component (about          R. Brown). Geological Survey of New South Wales, Report
25%) of nickel-hydride batteries and is replacing nickel–   GS1978/227 (unpubl.).
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Mischmetal is pyrophoric, and when scratched it gives       Industrial rocks and minerals, 6th edition, pp. 827–839.
off sparks capable of igniting flammable gases (Christie    Society for Mining, Metallurgy, and Exploration, Inc.,
et al. 1998). This property enables mischmetal to be used   Littleton, Colorado.
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                                                                Lynas Corporation Ltd 2002. Lynas doubles rare
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                                                                earth resource estimates for Mt Weld. Announcement to
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                                                                Australian Stock Exchange, 9 May 2002.
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