Scandium supply and demand: which comes first?
For those metals where a little goes a long way, a static market has led to a drop in competitive prices. Michael Forrest talks to George Putnam, CEO of EMC Metals Corp, USA, about the company’s plans to become a major scandium producer.
Speciality metals and rare earths have been regularly cropping up in news headlines of late, over concerns of supply to strategic industries. In truth, there is no shortage in the geological record, but the mine production of a number of these metals has become concentrated in a few locations where past investment or geological advantage has given producers a strong grip on supply – some in countries that are less politically stable than others. However, their overriding feature is small global consumption, which discourages new producers and in turn prevents the market from expanding, leading to increased production at more competitive prices. Very few of these speciality metals are mined in isolation – most are by-products or co-products of another commodity whose demand cycles may differ.
The effect of many of these elements on material processing goes way beyond the concentration in which they are alloyed or combined – for example, a few hundred parts per million of niobium transforms the strength of steel. Although many require complex processing and sell for a high unit price, the small amounts needed to enhance a material’s performance mean that their use does not have a major impact on the price of the final product.
One such element is scandium, which only occurs in major concentrations in three rare minerals – thortveitite, kolbeckite and bazzite – with concentrations in single minerals from 1–49%, and in ore from 1–5% scandium oxide. In rock-forming minerals, scandium is concentrated up to 100ppm in ferro-magnesium pyroxenes, amphiboles and dark micas, but is low or virtually absent in feldspars, olivines and quartz. World production is around 10 tonnes a year, which is entirely recovered from by-product processing of ores and tailings.
Such a small market belies the extent of scandium’s applications, says George Putnam, CEO of US speciality metals company EMC Metals Corp. ‘There are a number of applications that are already established, yet held back by the price and supply dynamics of scandium.’ One of its most prominent applications is an alloying agent in the production of aluminium. There are numerous patents on its strength-enhancing applications, underlined by its use in the development of Russian MiG fighter aircraft during the Cold War. Furthermore, its use in aluminium–scandium powder in additive manufacturing or 3D printing enables the production of near-shape technology lightweight components, with particular applications in the transport sector.
Scandium also performs as a zirconia electrolyte stabiliser in the manufacture of solid oxide fuel cells (SOFC). These cells enable the electricity generation in standalone units of various capacities, minus the noise or moving parts – ideal for auxiliary or backup power. As they do not combust fuel, these cells are cleaner as well as efficient in energy conversion greater than 65%. Their main attraction is the provision of distributed, inherently direct current (DC) power, which does not require connection to a grid and its associated power spikes. However, being capital intensive, the cells are most attractive to applications such as computer data servers and modern telephone systems that demand continuous service.
SOFCs are characterised by the oxidation of fuel (typically methane or biogas) and air into electricity. Comprising electrolyte, cathode and anode, they will produce a continuous power supply for as long as hydrocarbon gas is supplied. In modern SOFCs, a ceramic solid is used as the electrolyte component – a step forward from the corrosive liquid electrolytes of past-generation fuel cells. Zirconia/scandium-based cells offer high ionic conductivity alongside efficient energy generation.
The scandium search
‘We believe that the market for scandium can greatly increase once supply is assured and not dependent on co-production,’ says Putnam. To this end, EMC Metals Corp is developing a number of scandium projects, the most advanced of which is its 100%-owned Nyngan property in New South Wales, Australia. ‘This year, EMC was able to gain 100% of the project by acquiring the share of its joint venture partner, Jervois Mining,’ Putnam explains. The project is based on laterites overlying Alaskan-type mafic intrusives ranging from hornblende monozites, pryoxenites and hornblendites, to dunite-peridotites that are intruded into same-aged Cambrian-Ordovican metasediments of the Girilambone Group.
The Nyngan resource is contained within extensive laterite deposits of Tertiary to Recent-age that range from eight–50 metres thick (indicative of tropical weathering conditions) and has a typical profile of iron-rich clay, limonitic clay, saprolitic clay, weathered bedrock and fresh bedrock. Previous exploration at Nyngan focused on platinum, with extensive drilling revealing low-grade mineralisation. At the turn of the century a number of reverse-circulation drill traverses were undertaken for nickel, while air-core drilling as part of the regional programme by Jervois in 2005 revealed significant scandium mineralisation within the laterite. A further nine-hole drill was completed by EMC in 2008 to obtain samples for research, when the vertical orientation of the air-core drill confirmed the true widths of the lithologies.
Samples from these drilling programmes revealed significant scandium enrichment in the saprolite and limonite horizons. Drill samples, density profiles and geochemical analysis have determined a resource of 12Mt grading 261ppm using a 100ppm cut-off. This equates to more than 180 years’ supply at an expected production rate of 30t oxide a year. The company has a high-grade option – more than 350ppm for 20 years – which still maintains a 100-year resource. Putnam explains, ‘Although this resource is very big and of good grade, the key to the project comes down to controlling capital and operations expenditure’. The actual mining stage is a small part of the operation – the key is refining a high-quality product at the lowest possible cost, and building marketing contacts to maximise potential for expansion in the future.
Route to recovery
In 2012, EMC commissioned Hazen Inc, a US-based mineral laboratory, to determine a recovery route for the contained scandium oxide. The objective of the tests was to construct a semi-continuous pilot plant that would consolidate past work by Hazen, CSIRO and Metcon Laboratories for EMC and its (then) partner, Jervois Mining.
A 1.12-tonne sample at an average ore grade of 317ppm was subjected to conventional acid bake and solvent extraction techniques. Five sample batches were first subjected to 150 hours in a small rotary kiln before being water-leached to provide a primary filtrate of 1.9 tonnes (including water), with 73–83% recovery and 60ppm in solution. Next, a solvent extraction circuit using a variety of solutes, counter-current circuits and temperatures gave a primary product grading 890ppm scandium and recoveries of more than 99%. Finally, several precipitation and finish tests were performed to provide a marketable purity product with the highest possible recovery levels. All of the tests were single-pass within the semicontinuous framework, and overall recovery of scandium (as an oxide) was 70–80% with purity of 97.5%.
‘The reason for the focus on a high-purity product is demand from advanced aluminium alloys and SOFCs,’ explains Putnam. Like other rare metal additions, a little goes a long way and, given the investment in these components, this makes scandium demand relatively immune to price. This is just as well, as according to the United States Geological Survey, scandium oxide prices had increased over the past five years, with 99% oxide in some markets – an increase from US$1,400/kg to US$3,700/kg in 2012. In small quantities, 99.9% oxide can sell for in excess of US$5,000/kg – however, Putnam notes that there is no price for one-tonne lots of this material, and no one is offering that quantity. ‘Prices in excess of US$2,000/kg still allow scandium to be used in virtually all of its applications, while remaining economic, attractive and in demand.’