Department of Natural Resources and Mines
Geological Survey of Queensland
Indium opportunities in Queensland
September 2014
What is indium?
How do we use indium?
Indium is a chemical element with symbol In and atomic
number 49. This rare, very soft, malleable and easily fusible
heavy metal is chemically similar to gallium and thallium,
and shows properties that are intermediate between these
two. Indium was discovered in 1863 and named for the indigo
blue line in its spectrum that was the first indication of its
existence in zinc ores, as a new and unknown element. The
metal was isolated in the following year. Zinc ores continue
to be the primary source of indium, where it is found in
compound form. Very rarely the element can be found as
grains of native (free) metal, but these are not of commercial
importance.
The first large-scale application for indium was as a coating
for bearings in high-performance aircraft engines during
World War II. Afterward, production gradually increased
as new uses were found in fusible alloys, solders, and
electronics. In the 1950s, tiny beads of it were used for the
emitters and collectors of PNP alloy junction transistors.
In the middle and late 1980s, the development of indium
phosphide semiconductors and indium tin oxide thin films for
liquid crystal displays (LCD) aroused much interest. By 1992,
the thin-film application had become the largest end use.
Why indium is considered ‘critical’
Globally, most primary indium is recovered as a by-product
of processing zinc ores. As such it is considered as ‘at
risk’ because its supply is dependent on prices of other
commodities.
Global secondary indium production increased significantly
during the past several years and now accounts for a greater
share of indium production than primary. This trend is
expected to continue in the future. In 2007, several major
secondary indium producers in Japan and the Republic of
Korea announced plans to further increase their recycling
capacity. The indium market, however, remained in deficit as
demand for the metal, supported largely by indium tin oxide
(ITO) demand, continued to outpace supply. In 2007, year-onyear shipments of LCD television panels, which are a major
use of indium, were forecast to increase by 47%, and LCD
monitor panels to increase by 24%. Mainstream LCD devices
were also trending toward larger panel sizes, which require
more indium per unit.
Increased manufacturing efficiency and recycling (especially
in Japan) maintain a balance between demand and supply.
According to the United Nations Environment Programme,
indium’s end-of-life recycling rate is less than 1%. Demand
increased as the use of the metal in LCDs and televisions
increased, and supply decreased when Chinese mining
concerns stopped extracting indium from their zinc tailings.
In 2002, the price was US$94 per kilogram. Recent changes
in demand and supply have resulted in high and fluctuating
prices of indium, which from 2006 to 2009 ranged from
US$382/kg to US$918/kg.
It has been estimated that there are fewer than 14 years left
of indium supplies, based on current rates of extraction,
demonstrating the need for additional recycling .
Electronics
• Indium oxide (In2O3) and indium tin oxide (ITO) are used
as a conductive coating applied to glass substrates in the
making of electroluminescent panels.
• Some indium compounds such as indium antimonide,
indium phosphide, and indium nitride are semiconductors
with useful properties.
• Indium is used in the synthesis of the semiconductor
copper indium gallium selenide (CIGS), which is used for
the manufacture of thin film solar cells.
• Indium is used in light-emitting diodes (LEDs) and laser
diodes based on compound semiconductors that are
fabricated by Metalorganic Vapor Phase Epitaxy technology.
• Ultrapure metalorganics of indium include high purity
trimethylindium (TMI), which is used as a precursor in III-V
compound semiconductors, while it is also used as the
semiconductor dopant in II-VI compound semiconductors.
• Indium is one of many substitutes for mercury in alkaline
batteries to prevent the zinc from corroding and releasing
hydrogen gas.
Metal and alloys
• Ductile indium wire.
• Very small amounts used in aluminium alloy sacrificial
anodes (for salt water applications) to prevent passivation
of the aluminium.
• Indium is used as a conducting adhesive to bond gold
electrical test leads to superconductors, and applied under
a microscope with precision tweezers.
• In the form of a wire it is used as a vacuum seal and a
thermal conductor in cryogenics and ultra-high vacuum
applications, for example, in manufacturing gaskets which
deform to fill gaps.
• Used as a calibration material for differential scanning
calorimetry.
• It is an ingredient in the gallium–indium–tin alloy
Galinstan, which is liquid at room temperature while not
being toxic like mercury.
Other uses
• Indium tin oxide is used as a light filter in low pressure
sodium vapour lamps. The infrared radiation is reflected
back into the lamp, which increases the temperature within
the tube and therefore improves the performance of the
lamp.
• Indium’s melting point of 429.7485°K (156.5985°C) is a
defining fixed point on the international temperature scale.
• Indium’s high neutron capture cross-section for thermal
neutrons makes it suitable for use in control rods for nuclear
reactors, typically in an alloy containing 80% silver, 15%
indium, and 5% cadmium.
• In nuclear engineering, the (n,n’) reactions of 113In and 115In
are used to determine magnitudes of neutron fluxes.
• Indium is also used as a thermal interface material by
personal computer enthusiasts in the form of pre-shaped
foil sheets fitted between the heat-transfer surface of a
microprocessor and its heat sink. The application of heat
partially melts the foil and allows the indium metal to fill in
any microscopic gaps and pits between the two surfaces,
removing any insulating air pockets that would otherwise
compromise heat transfer efficiency.
•
In emits gamma radiation and is used in indium
scintigraphy, a technique of medical imaging that is
particularly helpful in identifying conditions such as
osteomyelitis.
111
Where is indium found?
Trace amounts of indium occur in base metal sulfides—
particularly chalcopyrite, sphalerite, and stannite—by ionic
substitution. Indium is most commonly recovered from the
zinc-sulphide ore mineral sphalerite. The average indium
content of zinc deposits from which it is recovered ranges
from less than 1 part per million to 100 parts per million.
Although the geochemical properties of indium are such that
it occurs with other base metals—copper, lead and tin—and
to a lesser extent with bismuth, cadmium, and silver, most
deposits of these metals are subeconomic for indium.
Vein stockwork deposits of tin and tungsten host the
highest known concentrations of indium. However, the
indium from this type of deposit is usually difficult to
process economically. Other major geologic hosts for indium
mineralisation include volcanic-hosted massive sulphide
deposits, sediment-hosted exhalative massive sulphide
deposits, polymetallic vein-type deposits, epithermal
deposits, active magmatic systems, porphyry copper
deposits and skarn deposits.
Where is indium found in Queensland?
Indium is known to occur with tin – base metal mineralisation
in vein deposits in the Irvinebank–Herberton and Mount
Garnet areas (for example, Arbouin, Black Sparkle, Isabel,
Orient Camp, Weinert, Baal Gammon, Khartoum).
Queensland’s known indium resources and reserves totalled
114,392 kilograms in 2012, but because it is not an element
that is usually assayed for, its full distribution is not known.
Polymetallic sulphide-tin deposits of the Hodgkinson
Province represent an important indium resource in
Queensland. Baal Gammon is now owned by Consolidated
Tin Mining Limited (previously owned by Monto Minerals
Limited). Mining at Baal Gammon commenced in March
2014 but production has now ceased. The deposit has
total indicated and inferred resources, according to Monto
Minerals in 2012, of 2.8 million tonnes of ore at 0.996%
copper, 0.199% tin, 40 grams per tonne (g/t) silver and 38 g/t
indium. These indium grades are amongst the highest in
the world although some indium would have been removed
during the mining phase.
Indium also commonly occurs with zinc in sphalerite.
Queensland is the third largest global producer of zinc,
however no production of indium is recorded.
Exploration potential in Queensland
The Hodgkinson Province in north Queensland has the
potential to be one of the world’s leading indium resources.
Further reading
http://minerals.usgs.gov/minerals/pubs/commodity/indium/
index.html#mcs
Further information
GSQ hotline
Email: [email protected]
Telephone: +61 7 3006 4666
Geological Survey of Queensland
Level 12, 61 Mary St Brisbane Qld 4000
www.dnrm.qld.gov.au
140°
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Cooktown
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Produced by Publication Graphics SGS, Geological Survey of Queensland September 2014.
© State of Queensland (Department of Natural Resources and Mines) 2014.
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Produced by Spatial and Graphic Services, Geological Survey of Queensland
© The State of Queensland (Department of Natural Resources and Mines) 2014
http://creativecommons.org/licenses/by/3.0/au/deed.en
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