LONDON, July 26 (Reuters) - Scandium sits in the shadows of the periodic table. Even by the esoteric standards of other critical minerals, the soft, silvery metal with the atomic number 21 is something of an enigma.
The global market is thought to be somewhere between 15 and 25 tonnes in size, but no one is very sure. Production is potentially a lot higher. It's difficult to say, however, since much of it is in China and production is always as a by-product of other metals.
Russia used scandium-aluminium alloys in its MIG fighter jets as early as the 1980s. It, too, has scandium production.
The United States, by contrast, has been wholly reliant on imports in recent years. It is typical of scandium's opacity that the United States Geological Survey (USGS) says there is "no definitive data" on suppliers.
Imports are "thought to be mostly from Europe, China, Japan and Russia", the USGS says.
It's not hard to see why scandium is on the U.S. critical minerals list.
It turns out, though, that Rio Tinto has been producing scandium all along at its titanium operations over the Canadian border. But the metal now deemed critical was going with other waste into a tailings pond.
The company has now worked out how to extract scandium oxide from the titanium processing stream, making it North America's sole producer.
Rio Tinto has just performed the same trick for another critical mineral - tellurium - at its copper smelter in Utah.
Mine and processing waste is fast emerging as a new frontier for critical metals supply.
THE 'IF' METAL
Scandium, according to the Minor Metals Trade Association (MMTA), has long been considered an "if" metal. ("Scandium emerges from the shadows" https://mmta.co.uk/2022/04/05/scandium-emerges-from-the-shadows, April 5, 2022)
If only there were enough supply, particularly Western supply, manufacturers would have exploited its qualities as an alloying agent with aluminium.
Throw a tiny amount of scandium into the aluminium melt and you get 10-15% weight reduction, higher strength, greater flexibility and resistance to thermal shock.
All characteristics that make it perfect for high-performance aircraft or aerospace applications.
However, for want of accessible supply, scandium-aluminium alloys have been confined to niche Western products such as baseball bats and lacrosse sticks.
Rio Tinto Fer et Titane will change that by ramping up its commercial-scale demonstration plant in Quebec to nameplate capacity of three tonnes a year, which may not sound much but is equivalent to about a fifth of global supply.
The project took less than two years from drawing board to commercial demonstration, needs no extra mining and comes with a low carbon footprint.
TURNING SLIME INTO SOLAR PANELS
Tellurium is another critical mineral headache for the United States. Import reliance is more than 95%, the USGS says.
China is the world's dominant producer, extracting tellurium from metallic waste streams. Global production was only 580 tonnes in 2021, according to Rio Tinto.
Lying on what the MMTA describes as "the boundary of metals and non-metals", tellurium demand is spread across a broad spectrum of specialist applications.
However, its use via cadmium telluride in solar panels makes it an important and fast-growing energy transition metal.
First Solar, the largest U.S. photovoltaic panel producer, will be a customer of Rio Tinto's Kennecott copper smelter-refinery in Utah.
The tellurium was previously part of Kennecott's anode slime waste stream, destined for treatment and long-term storage.
Now it will be converted into copper-tellurium at a rate of 20 tonnes a year before being sent to Canada's 5N Plus for refining and onward supply to First Solar. 5N Plus will also use some of the material for ultra-high purity semiconductor materials at its Utah facility.
Kennecott's new tellurium circuit cost only $2.9 million and took less than three years to build after the local team started measuring sufficiently high concentrations in the copper ore in 2019.
TOTAL MINING
Both these projects are transformative, de-risking two of the United States' critical mineral supply chains.
Neither requires an extra tonne of mined rock, obviating the need to engage in what is often a tortuous planning and authorisation process.
They are examples of a new industry trend towards so called whole-concept mining, also known as total mining, broadening a historical focus on one or two primary products to potentially everything of metallic value in the ore being mined and processed.
"Kennecott's tellurium plant is the latest example of work we're doing globally to minimise waste by finding a use for every material we dig from the ground or creating new products from the waste itself," Rio Tinto says.
Producers the world over are going back to their processing sheets to understand better what they have previously been throwing in the waste pond.
Russian aluminium producer Rusal, for instance, has found its own way of making scandium from the "red mud" waste generated in the alumina refining process.
It launched its ScAlution range of scandium alloys last year, aspiring to capture a share of a market that could grow to 300,000 tonnes a year by 2035 thanks to improved supply.
The next big waste-to-minerals challenge is lithium, the metal that sits at the very heart of the green energy transition.
Rio Tinto is working on a project to produce lithium from 90 years of waste accumulated at its Boron mine site in California and others are following the same path, targeting old coal-mining districts as a potential source of lithium and other energy transition metals such as cobalt and manganese.
The USGS has been tasked with mapping and collecting data for areas containing mine waste "to increase understanding of above-ground critical mineral resources in previously disturbed areas".
It's not only a highly cost-effective way of closing the country's critical minerals gaps, but also a way of closing the green-on-green divisions that cause every new energy transition metals mine to run into fierce environmental opposition.
The green future, it turns out, can be achieved at least in part by cleaning up the mining legacy of the past.
Andy Home is a Reuters market analyst. The views expressed are his own.
