According to Dr Laurie Hutton, Director—Exploration Attraction, Geological Survey of Queensland, scandium—currently used in high-tech bike frames and TV floodlights—is attracting attention as Queensland becomes a likely producer. Until now, scandium was recovered as a byproduct from uranium leaching in the USA and Russia. However, two recent discoveries in Queensland and one in New South Wales may provide a reliable supply of scandium to the market. Metallica Metals reported at the Mining 2011 conference that two of the world’s three defined scandium resources are in Queensland. The SCONI deposits (previously NORNICO) are held by Metallica Minerals at its Lucknow deposit south of Greenvale (6.24 Mt @ 169 g/t Sc for 1,580 t of Sc2O3) and the Kokomo deposit further north (8.9 Mt @ 109 g/t Sc for 1,500 t of Sc2O3).The third defined deposit is in New South Wales. Present prices are >$1,500/kg Sc2O3.
The distribution of scandium in Queensland was tested during a regional national geochemical survey. The survey shows several drainage systems in Queensland with anomalous scandium concentrations in the sediments. At this stage there has been no testing to determine its source. One possible scenario is that the streams sampled drain laterite profiles which can concentrate the mineral. These data suggest that there is potential for more discoveries in Queensland if the predicted surge in demand for scandium eventuates. As scandium is also concentrated along with other rare earth elements (REE), exploration for the two commodities could go hand in hand.
Scandium (atomic number is 21) is one of several strategic elements that have not been exploited in significant quantities, but which are now attracting new interest because of likely new sources and its potential use in new technologies.
Scandium is not technically one of the rare earth elements; however, the International Union of Pure and Applied Chemistry includes scandium as the lightest member in its REE definition. It is included with a group of elements such as yttrium, which is also included in the rare earths. It is a silverish-whitish metal that turns yellowish or pinkish when exposed to air. Scandium has a melting point of 1,541oC.
Scandium is rarely found concentrated in a natural form because it lacks affinity to combine with common ore-forming anions, therefore mineral deposits containing significant concentrations are rare. It is more abundant on the Moon than it is on Earth!
Scandium’s low production levels have restricted its usefulness, but likely future increased production will lead to more research and wider use.
Regular supply, such as that predicted to come from Queensland, will see the scandium use increase and become more common.
Currently, scandium is used in:
- Bicycle frames and golf clubs – In scandium–aluminium alloys a small amount of scandium significantly increases the strength and corrosion resistance of the alloy. Such light, high strength alloys are currently mainly used in high performance sporting goods such as baseball bats, bicycle frames or golf clubs
- Advanced fuel cell technology – In the manufacture of solid oxide fuel cells which chemically convert natural gas (or other fuels) into electricity, scandium oxide produces the most efficient cells at lower temperatures. These cells provide more efficient on-site electricity and heating and produce less carbon dioxide than conventional fuel cell technology
- Lighting for film and television – High intensity discharge lamps use scandium iodide to create a light that is similar to daylight. Scandium lights are used on film sets or sporting arenas to improve television pictures because of the light quality and because they are more efficient than other high intensity lights. The USA uses 20 kg of scandium a year to create high intensity lights
- Fighter jets and hand guns – Scandium alloy is also used to make high strength hand gun frames for the same reason it is used in sporting goods—it is light and strong. Russia uses the scandium–aluminium alloy in the frames of its MiG fighter airframes. This use is likely to be more common as supplies of scandium increase
- Defence and dentistry – Laser crystals of gadolinium scandium (or gallium garnets) are used in strategic defence applications and in dental lasers.
Scandium has a crustal abundance of ~25ppm. It has a higher concentration in mafic rocks (~30–40 ppm in basalt) than in intermediate rocks (~10–30 ppm in andesite) and <10ppm in granites. Granite pegmatite often contains minerals enriched in Sc, particularly in minerals such as beryl, garnet and xenotime. High concentrations are described from ore minerals from Sn-W deposits (Kempe & Wolf, 2006) with concentrations up to several thousands ppm in wolframite and cassiterite, even though the enclosing granites have low concentrations typical of granites. Enrichment in these systems is interpreted by Kempe & Wolf (2006) to be from an external F-rich fluid carrying also uranium and heavy REE and possibly derived from a mantle source.
Scandium is found in the minerals thortveitite, euxenite, and gadolinite, which are rare and are believed to be magmatic in origin and occur in association with fluorite-bearing granitic pegmatite.
Scandium is often concentrated in laterite profiles in humid tropical environments. Absorption on clay minerals is a primary source for enrichment. The element is generally associated with siderophile elements like iron (Fe), chromium (Cr), and cobalt (Co). Elevated scandium is found at the Bayan Obo laterite deposit in Mongolia (Shimazaki & others, 2008).
Read more
Kempe, U, & Wolf, D, 2006, Anomalously high Sc contents in ore minerals from Sn-W deposits: Possible economic significance and genetic implications. Ore Geology Reviews, 28, pp 103-122.
Shimazaki, H, Yang, Z, Miyawaki, R, & Shigeoka, M, 2008, Scandium-bearing minerals in the Bayan Obo Nb-REE-Fe deposit, Inner Mongolia, China. Resource Geology, 58, pp 80-86.