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RARE EARTH ELEMENTS
Potential and Outlook
New South Wales has excellent potential for
commercial deposits of rare earth elements, principally
in trachyte intrusions of Mesozoic age. The Toongi
prospect (Toongi) (Figure 22), which is one of
numerous intrusions in the central west of New South
Wales, is a potentially world-class source of rare earth
elements. This intrusion is about 24 km south of
Dubbo and consists of hydrothermally altered alkali
trachyte with anomalous rare metal and rare earth
elements, principally zirconium oxide, niobium/
tantalum oxide and yttrium oxide.
Beach placers along much of the coast north of Sydney
have heavy mineral assemblages that are dominated
by rutile and zircon, and minor amounts of monazite.
These deposits are largely depleted, uneconomic or not
accessible. The rare earth potential of heavy minerals
sands deposits in the Murray Basin, which have small
proportions of monazite and xenotime, has yet to be
fully assessed.
Nature and Occurrence
The rare earth elements (REE) are the 15 lanthanide
elements with atomic numbers 57 to 71 (Christie
et al. 1998). In order of increasing atomic number,
they are lanthanum (La), cerium (Ce), praseodymium
(Pr), neodymium (Nd), promethium (Pm), samarium
(Sm), europium (Eu), gadolinium (Gd), terbium (Tb),
dysprosium (Dy), holmium (Ho), erbium (Er), thulium
(Tm), ytterbium (Yb) and lutetium (Lu). Yttrium (Y),
scandium (Sc) and thorium (Th) are generally included
with the REE as they occur with them in minerals and
have similar chemical properties.
REE are classified into two groups: light REE or cerium
group (lanthanum to europium) and the heavy REE,
comprising gadolinium through lutetium, as well
as yttrium and scandium. The light REE are more
abundant than the heavy REE.
The term ‘rare earths’ was proposed in 1794 (Christie
et al. 1998). The term ‘rare’ was used because when
they were found they were thought to be present in
the Earth’s crust in only small amounts, and ‘earths’
because as oxides they have an earthy appearance.
Despite their name, the REE are each more common
in the Earth’s crust than silver, gold or platinum, while
cerium, yttrium, neodymium and lanthanum are more
common than lead.
The elemental forms of REE are iron-grey to silvery
lustrous metals (Harben 1999). Typically, they are soft,
malleable and ductile, and usually reactive (rapidly
forming rare earth oxides), especially at higher
temperatures or when finely disseminated. REE are
never found as free metals in rocks. They typically
occur as mixtures of various REE-bearing minerals
and require mineral separation from each other for
commercial use.
Bastnaesite, (Ce,La)(CO3)(OH,F); xenotime, YPO4; and
monazite, (Ce,La,Nd,Th)PO4.SiO4 are the three most
economically significant minerals of the more than
200 minerals known to contain essential or significant
REE (Christie et al. 1998). Bastnaesite and monazite
are sources of light REE and account for 95% of REE
currently used (Harben & Kuzvart 1996). Xenotime
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
properties to the monazite.
In 2004, global production of rare earths was about
102 000 tonnes, mainly from bastnaesite and monazite
deposits, some 90 000 tonnes of which came from
China (Hedrick 2005). Other producers of REE
included Russia, India, Malaysia and Sri Lanka. Global
resources of rare earths are estimated at 88 million
tonnes (about one third held by China), primarily in
bastnaesite and monazite. Hedrick (2005) concluded
world rare earth resources are very large compared to
their expected demand.
Deposit Types
REE minerals occur in a diverse range of igneous,
sedimentary and metamorphic rocks (Sawka et al.
1990; Harben & Kuzvart 1996; Jones et al. 1996;
Christie et al. 1998). Their principal geological
environments are summarised below.
1. Carbonatites: carbonate-rich rocks of magmatic
origin are commonly associated with major faults,
lineaments and explosive volcanism. Typically
the last magmatic stage in alkaline–carbonate
150°00’E
155°00’E
TWEED HEADS
BYRON BAY
TENTERFIELD
LIGHTNING RIDGE
N
MOREE
INVERELL
GRAFTON
0
100
30°00’S
kilometres
30°00’S
NARRABRI
COFFS HARBOUR
ARMIDALE
REFERENCE
Rare earth occurrence - monazite
TAMWORTH
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.
155°00’E
150°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
nephelinites). Bastnaesite-bearing carbonatite is
the world’s main source of REE. Examples of REEbearing carbonatite deposits include Bayan Obo in
Inner Mongolia, China; Mountain Pass, California;
and the Mineral Hill district, Idaho–Montana.
2. Beach placers containing detrital REE minerals
of high specific gravity, principally monazite and
xenotime. These minerals are extracted from beach
placers that are mined primarily for their rutile,
zircon and ilmenite contents. Examples include
eastern and western Australia; Florida and Georgia
in the USA; South Africa; India; and Sri Lanka.
3. Peralkaline syenitic and granitic igneous rocks are
characterised by the occurrence of alkali amphibole
and pyroxene minerals. REE minerals, principally
eudialyte, Na(Ca,La)2(Fe,Mn,Y)ZrSi8O22(OH,Cl)2,
and loparite, (Ln,Na,Ca)(Ti,Nb)O3, form as
magmatic deposits in the host igneous rocks, and
as metasomatic deposits in veins, stockworks and
irregular replacement zones. Examples include the
Kola Peninsula, Russia; and the Brockman deposit,
Western Australia.
4. Iron–REE deposits, perhaps the largest being the
Olympic Dam (South Australia) hematitic granite
breccia-style (IOCG) deposit. This is a very large
deposit, in the order of several thousand million
tonnes, that consists of disseminated chalcopyrite,
bornite and chalcocite accompanied by gold,
uranium, silver, barium, REE and fluorine minerals
(Christie et al. 1998). Extremely fine-grained
monazite and bastnaesite are the most common
REE minerals at Olympic Dam, which contains
0.2% La and 0.3% Ce.
5. Pegmatites, hydrothermal quartz and fluorite veins
of various origins. Examples include Northern
Territory, Australia (pegmatites); Karonge, Burundi
(hydrothermal quartz); and Naboomspruit, South
Africa (fluorite veins).
6. Skarn deposits (not associated with carbonatites),
which include the Mary Kathleen U–REE–Th
skarn, Queensland (now mined out). This deposit
contained REE minerals hosted in uraninite, apatite
and allanite developed in garnet-bearing calcsilicate
rocks near an alkali granite intrusion.
7. Residual laterites enriched in REE that formed by
intense subtropical weathering of REE-rich alkaline
complexes. These deposits occur predominantly as
mineral assemblages of goethite, hematite, aluminium
hydroxides, kaolinite minerals and quartz, and
typically contain 10% to 25% rare earth oxides (REO).
8. Residual deposits of REE-bearing clays, termed ionic
or ion-adsorption type ores, develop in association
with weathered granites. Ion-adsorption ores
are only known from China (Long Nan, Yianxi,
southern China). Rare earth cations released during
weathering of granites were adsorbed by kaolin and
various aluminosilicates. They have grades of about
1% REO and are characterised by very low cerium
content and a rare earth content that is rich in
samarium, europium and terbium, or yttrium.
Main Australian Deposits
Australia was formerly the world’s largest producer of
monazite, almost entirely from beach placer deposits
in New South Wales, Queensland and Western
Australia (Harben & Kužvart 1996). There has been
no commercial production of monazite from those
sources since 1995 (ABARE 2001). There are several
deposits in Western Australia, the Mount Weld deposit
and Brockman deposit (see following discussion).
Production has yet to begin at either deposit (late 2005).
Mount Weld, Western Australia, is a major REE
deposit that is developed in laterites formed on
a carbonatite diatreme of Palaeoproterozoic age
(Fetherston 2002). REO contents up to 40% have been
found in the laterites. Mount Weld has resources
of 7.7 Mt at a grade of 11.9% rare earth oxides,
which represents about 917 000 tonnes of rare earth
oxides (Lynas Corporation Ltd 2002, 2003). Mining
operations began in mid 2007.
The Brockman deposit, Western Australia, is a
potential source of tantalum–niobium and heavy REE
(Castor 1994). The REE occur as very fine-grained
minerals disseminated in metamorphosed rhyolitic tuff
hosted by hydrothermally altered trachyte. The deposit
contains a resource of 50 million tonnes at 4400 ppm
Nb2O5, 270 ppm Ta2O5, 1240 ppm Y2O3, 110 ppm Ga,
350 ppm HfO2, 900 ppm REE and 1.03% ZrO2 (Aztec
Resources Limited 2005).
New South Wales Occurrences
In the central western part of New South Wales,
mainly north of Rylstone (near Mudgee) and south of
Dubbo (Figure 22), there are numerous Mesozoic sills,
laccoliths, dykes and flows (Warren et al. 1999). They
range in composition from basalt to alkali diorite to
trachyte, syenite and phonolite. The intrusions appear
structurally controlled and are aligned along largescale lineament sets. In New South Wales, trachyte
intrusions appear to have the greatest potential for
commercial occurrences of REE.
The Toongi prospect (Toongi), which is about 24 km
south of Dubbo (Figure 22), is a small, altered
alkali trachyte intrusion of Triassic age containing
anomalous rare metal and rare earth elements
(Chalmers 1999; Alkane Exploration Ltd 2004).
Hydrothermal alteration involving significant
carbonate, chloritic, potassic and argillic alteration has
modified the Toongi prospect (Downes 1999). The REE
mineral assemblage is very fine-grained and includes
bastnaesite, zirconium silicate, yttrium silicates and
niobium–tantalum silicates.
Toongi, also known as the Dubbo Zirconia Project, has
resources of 73.2 Mt @ 1.96% ZrO2, 0.04% HfO2, 0.46%
Nb2O5, 0.03% Ta2O5, 0.14% Y2O3 and 0.745% total REO
(Alkane Exploration Ltd 2004). Feasibility studies
envisage production of 200 000 tonnes per annum of
ore to produce 3000 tonnes of zirconium, 600 tonnes
of niobium and tantalum and 1200 tonnes of yttrium–
rare earth products.
Lateritic nickel, cobalt and scandium resources have
been identified at Lake Innes, near Port Macquarie
(Figure 22) (Douglas McKenna & Partners Pty Ltd
2003). Serpentinite complexes occur in a Permian fault
zone in Silurian–Devonian rocks. Locally, over the
serpentinite complexes, laterites, containing weathered
serpentinite, saprolite, limonitic clay and hematite
clay, range in thickness from 10 m to 30 m. Scandium
tends to occur in the upper part of the lateritic profile,
whereas cobalt and nickel are found in the middle
and lower parts of the profile. The deposits contain
15.7 million tonnes of nickel at 1.46% nickel, 0.09%
cobalt and 41 ppm scandium.
Alkali pyroxenite rocks from the Staurolite Ridge
intrusion, Broken Hill, contain altered ultrabasic
rocks with high (about 35%) granoblastic carbonate
(Barron 1978). The potential in New South Wales
for carbonatite-hosted REE minerals, however, is
unknown. There may be some potential for REE
deposits in A-type granites, and also A-type volcanic
rocks (L.M. Barron pers. comm., 2004). A-type
granites are highly evolved granites in which fluids
enriched in REE, elements such as Nb, Ta, Zr, Hf, Th, U
and Y, and volatiles such as F, P and CO2, accumulated
late during their formation (Sawka et al. 1990). In New
South Wales, A-type granites are associated with the
Bega Batholith and Wyangala Batholith, and A-type
volcanic rocks with the Comerong and Boyd volcanic
complexes (Chappell et al. 1991).
in applications such as cigarette lighters, miners’ safety
lamps and automatic gas-lighting devices.
Applications
Several very large deposits, including Mianing in
China, the Mount Weld deposit in Western Australia
and the Dubbo Zirconia Project, have yet to be
fully developed. Long-term demand for monazite is
expected to increase because of its abundant supply
and its recovery as a low-cost by-product of mineral
sands mining.
Rare earths have numerous, diverse, highly specialised
applications (Christie et al. 1998; Hedrick 2005). The
largest use of rare earth oxides is in mixed forms,
principally in petroleum fluid-cracking catalysts and in
rare-earth phosphors for television, X-ray intensifying,
and fluorescent and incandescent lighting. These forms
are listed below.
• Globally, about 35% of REE are used as catalysts,
mainly in the refining of crude oil to improve
cracking efficiencies and in automobiles to improve
oxidation of pollutants.
• Some 30% of REE are used in the glass and
ceramics industry as glass-polishing compounds,
decolourising agents, UV absorbers, colouring
agents, in optical lenses and glasses, and additives
to structural ceramics — such as stabilised zirconia
and silicon nitride.
• About 30% of REE are used in metallurgy as
an alloying agent to desulphurise steels, as a
nodularising agent in ductile iron and as lighter
flints. REE are also used as alloying agents
to improve the properties of superalloys and
magnesium, aluminium and titanium alloys.
Other uses of REE include lasers, microwave applications,
alloys, computer memory and specialised ceramics
(Harben & Kužvart 1996). Rare earths enable glass fibres
to transmit information over long distances without
booster stations. Samarium–cobalt batteries have largely
replaced more expensive platinum–cobalt batteries.
Mischmetal, an alloy composed of Ce, La, Nd, Pr, Sm,
Tb and Y and iron, about 5%, is a component (about
25%) of nickel-hydride batteries and is replacing nickel–
cadmium batteries in portable electronic equipment.
Mischmetal is pyrophoric, and when scratched it gives
off sparks capable of igniting flammable gases (Christie
et al. 1998). This property enables mischmetal to be used
Scandium is used mainly as a component of
aluminium alloys in baseball and softball bats; as
alloys, compounds and metals in metallurgical
research; sporting goods equipment; semiconductors; and speciality lighting (Hedrick 2005).
Overall, scandium consumption is very small.
Yttrium is primarily used in lamp and cathode
phosphors and lesser amounts in structural
ceramics and oxygen sensors.
Economic Factors
There is an expanding market for rare earths. Their
use in automobile pollution catalysts, permanent
magnets and rechargeable batteries, should increase
(Hedrick 2005). Strong demand for cerium and
neodymium for use in automobile catalytic converters
and permanent magnets is expected to continue over
the next five to ten years. Future demand is likely for
rare earths in rechargeable batteries, fibre optics and
various medical applications. Long-term growth is
expected for rare earths in magnetic alloys for such
uses as electric generators and air conditioners.
References
ABARE 2001. Australian commodity statistics 2001.
Australian Bureau of Agricultural and Resource Economics
(ABARE), Canberra.
Alkane Exploration Ltd 2004. Annual Report 2004.
www.alkane.com.au
Aztec Resources Limited 2005. Latest News.
www.aztecresources.com.au
Barron B.J. 1978. Unpublished petrological report No.
78/22: petrographic features of alkali pyroxenite rocks
from the Staurolite Ridge intrusion Broken Hill N.S.W.
(in conjunction with mapping of the Pinnacles sheet by
R. Brown). Geological Survey of New South Wales, Report
GS1978/227 (unpubl.).
Castor S.B. 1994. Rare earth minerals. In: Carr D.D. ed.
Industrial rocks and minerals, 6th edition, pp. 827–839.
Society for Mining, Metallurgy, and Exploration, Inc.,
Littleton, Colorado.
Chalmers I. 1999. Dubbo zirconia project. Minfo—New
South Wales Mining and Exploration Quarterly 62, 38–40.
Chappell B.W., English P.M., King P.L., White A.J.R. &
Wyborn D. 1991. Granites and related rocks of the Lachlan
Fold Belt. 1:250 000 scale map, Bureau of Mineral Resources,
Geology and Geophysics, Canberra, Australia.
Christie T., Brathwaite B. & Tulloch A. 1998. Mineral
commodities report 17 — rare earths and related elements. New
Zealand Institute of Geological and Nuclear Sciences Ltd.
Douglas McKenna & Partners Pty Ltd 2003. Final
report on Exploration Licences 4964, 5185, 5135 Lake Innes,
N.S.W. Nickel/cobalt/scandium laterite project. Report
prepared for Jervois Mining Limited. Geological Survey of
New South Wales, File GS2003/312. (unpubl.).
Downes P.D. 1999. Mineral occurrences. In: Meakin N.S.
& Morgan E.J. compilers. Dubbo 1:250 000 Geological
Sheet SI/55–4, 2nd edition. Explanatory Notes, pp. 396–426.
Geological Survey of New South Wales, Sydney.
Fetherston J.M. 2002. Industrial minerals in Western
Australia: the situation in 2002. Geological Survey of
Western Australia, Record 2002/12, 38.
Harben P.W. 1999. The industrial minerals handybook, 3rd
edition. Industrial Minerals Information Ltd, London.
Harben P.W. & Kužvart M. 1996. Industrial minerals: a
global geology. Industrial Minerals Information Ltd, London.
Hedrick J.B. 2005. Rare earths. In: United States Geological
Survey. compiler. Mineral Commodity Summaries 2005,
pp. 132–133. United States Department of the Interior.
Jones A.P., Wall F. & Williams C.T. eds. 1996. Rare earth
minerals: chemistry, origin and ore deposits. Chapman and
Hall, London.
Lynas Corporation Ltd 2002. Lynas doubles rare
earth resource estimates for Mt Weld. Announcement to
Australian Stock Exchange, 9 May 2002.
Lynas Corporation Ltd 2003. Lynas Corporation Ltd: an
emerging diversified resources company with a special link
to China. AGM 26 November 2003.
Sawka W.N., Heizler M.T., Kistler R.W. & Chappell
1990. Geochemistry of highly fractionated I- and S-type
granites from the tin–tungsten province of Western Australia.
In: Stein H.J. & Hannah J.L. eds. Ore-bearing granite systems:
petrogenesis and mineralizing processes, pp. 161–179.
Geological Society of America, Special Paper 246.
Warren A.Y.E., Barron L.M., Meakin N.S., Morgan E.J.,
Raymond O.L., Cameron R.G. & Colquhoun G.P. 1999.
Mesozoic igneous rocks. In: Meakin N.S. & Morgan E.J.
compilers. Dubbo 1:250 000 Geological Sheet SI/55–4, 2nd
edition. Explanatory Notes, pp. 313–328. Geological Survey
of New South Wales, Sydney.