Scandium, A Rare Earth That’s Not Really A Rare Earth?

August 03, 2011

While found in small quantities, scandium is scattered plentifully throughout the world.

 

As has been explained in the press, ad nauseam, over the past several years, rare earth metals are most commonly defined as the 17 “like elements”: 15 chemically comparable lanthanides (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), together with scandium and yttrium, neither of which is a lanthanide, and both of which appear elsewhere in the Periodic Table.

 

 

In addition to the similarity of its chemical characteristics with those of the lanthanides, scandium is often found in the same minerals in which the other rare earth metals exist.  The metal is also fiendishly difficult to isolate - as an element - in its pure form.  That said, however, its properties are also very akin to those of both aluminum and yttrium. 

Back in the late 19th century, scandium was another of those elements that — along with the likes of gallium, germanium and rhenium — the Russian chemist Dmitri Mendeleev predicted when he constructed the periodic table but, at the time, had yet to be “discovered.”  In scandium’s instance, Mendeleev named the predicted element “ekaboron” and reckoned its atomic number as being between 40 and 48.

It was only in 1879, some 10 years later, that the Swedish chemist Lars Fredrik Nilson was actually able to produce a tiny amount — just a couple of grams — of scandium oxide and named it scandium, after his native Scandinavia.  And, it was only in 1960 that a pound of the metal of 99 percent purity was actually created.

Whence Scandium?

There’s actually quite a lot of scandium spread widely about. It’s ranked as the 50th most common element on Earth and 23rd in the Earth’s crust.  However, rather like a number of the other strategic metals, it rarely occurs in any significant concentrations terrestrially and, according to one source, there are no known scandium primary deposits, i.e., containing more than 100 grams per tonne of scandium.

In fact, it’s more common in the Sun than it is on Earth.  Scandium never occurs on Earth in its free metallic form.

According to the United States Geological Survey, it “forms solid solutions [!] in more than 100 minerals,” and in the Earth’s crust, it “is primarily a trace constituent of ferromagnesium minerals.”

In nature, it is to be found, in particular, in the following: aluminum phosphate minerals; amphibole-Hornblende; basalt; beryl; biotite; cassiterite; columbite; gabbro; garnet; muscovite; pyroxene; rare earth minerals, and wolframite.

In addition, scandium is to be found in such rare minerals as  bazzite; euxenite; gadolinite; ixiolite; kolbeckite; magbasite; perrierite, and thortveitite.

According to one source, there are more than 800 minerals in which scandium can be found in “small quantities.”

However, rather than being extracted from these “raw” minerals, “primary” scandium has most commonly been produced either from mine tailings and residues containing the element, or as a byproduct from the processing of a variety of different ores.

Tailings and residues have included those from fluorite, moly, tantalum, titanium, tungsten and uranium mining operations.  In China, in particular, scandium has also been, and is, produced as a by-product of the extraction of rare earth metals.

 

 

Scandium is also to be found, in minute quantities, in the following ores: aluminum, cobalt, iron, nickel, phosphate, tin, zinc and zirconium, as well as in certain low-grade coals.

And reports have appeared, once more, in the press recently of the possibility of extracting scandium (together with cobalt and nickel) from laterites in North Queensland, Australia. 

Back in 2008, A.V. Naumov, in an article entitled “Review of the World Market of Rare-Earth Metals” in the Russian Journal of Non-Ferrous Metals, produced a fascinating little table indicating just how much scandium was extracted from the Earth’s surface along with “other mined minerals”.

Even though the figures today will be significantly different (and current opinion is that ilmenites are no longer a source of scandium), it does illustrate just how much of the metal is actually out there — if it could be recovered easily.  (And this does not even include any “primary” scandium production such as that mentioned above.)

Ore Processing – M Tonnes/Yr Accompanying Sc – Tonnes/Yr
Bauxites 71 710-1420
Uranium 50 50-500
Ilmenites 2.0 20-40
‘Tinstones’ (Cassiterites) 0.2 20-25
Zircons 0.1 5-12

Source: Russian Journal of Non-Ferrous Metals

Major Applications

There are currently three (and few other) major applications for scandium:

  • Fuel Cells:  Scandium is used as a dopant of zirconia (ScSZ) in Solid Oxide Fuel Cells (SOFCs).  Used thus, the metal increases both the lifespan and efficiency of the cells, and reduces their operating temperature.  Such cells have the “highest output potential of all electrolyte-supported fuel cells,” not least because ScSZ cathodes have the highest ionic conductivity of any of the options available for use in low temperature SOFCs. 

    Will this use for scandium take off?  There are doubts on at least two fronts: 1) the acceptance and future commercialization of fuel cells (SOFCs in particular); and, 2) the use of ScSZ in such cells.

  • Aluminum-Scandium (Al-Sc) Alloys:  While most of the Al-Sc alloy used today is to be found in leisure and sporting goods, e.g., bicycle frames, baseball bats, golf clubs, hand guns, tent poles and lacrosse sticks, other environments for its use continue to be actively researched.  The aircraft industry is one particular example.  (It was, once, used in both Soviet fighter planes and the nose cones of Soviet missiles.)  Not only are Al-Sc alloys suitably strong, they are also lighter and more corrosion-resistant than other, comparable aluminum alloys. In addition,  using weld wires incorporating scandium has some significant attractions, especially because of the increased strength and reduced susceptibility to heat cracking.  With both its strength and lightness, there are probably also some interesting opportunities for scandium in the automotive market, such as in the manufacturing of both engines and bodies.

    Despite its obvious attractions, whether scandium actually comes to be used extensively in the likes of the automotive and aero industries remains to be seen.  There are a couple of major drawbacks to its use in these contexts: current cost and current supply.  The former is high and the second is severely constrained. 

  • Lighting: The addition of scandium iodide (ScI3) to mercury vapor lamps enables their light to resemble natural sunlight closely.  With the increasing use of LEDs, though, there is a good possibility that the future of such lamps is not assured.


Scandium Production

Figures for scandium production are notoriously difficult to find, if, indeed, they exist at all.  The primary source of the element, estimated by one aspiring market participant to be 3.5 tonnes per annum, is in oxide form from old Soviet stockpiles.  (The former Soviet Union seems to have produced loads of the stuff.) 

Other sources of the metal — in oxide form and as a byproduct (around 2.5 tonnes per annum of scandium oxide )—have been given variously as Bayan Obo in China, the Zhovti Vody mine in Ukraine (formerly partially owned by the now-bankrupt Canadian company Ashurst) and apatite mines on Russia’s Kola Peninsula.  There is, however, significant doubt as to whether there is actually any production coming out of Zhovti Vody in Ukraine. It appears the mine was flooded a decade or more ago and has not produced any scandium since then.

 

 

According to the USGS: “Domestically, scandium-bearing minerals have not been mined or recovered from tailings since 1990.”  That having been said, there are abundant scandium-containing tailings (and, thus, scandium) available in the United States, particularly (again according to the USGS) in the “process residues from tungsten operations.”

In terms of the Earth’s scandium resources, the USGS states that: “Undiscovered scandium resources are thought to be very large.”  In the second edition of his Materials Handbook, published in 2008 by Springer-Verlag, London, François Cardarelli states that: “Proven mineable scandium reserves are 7.38 million tonnes of raw ore, corresponding to ca. 775 tonnes of proven reserves of scandium.”

Current global consumption is currently estimated to be 5-6 tonnes per annum. 

Some suppliers of scandium metal and scandium compounds include: Absco Materials; Alfa Aesar (part of Johnson Matthey); Atlantic Equipment Engineers (part of Micron Metals); GFS Chemicals; Goodfellow (part of the Goodfellow Group); Materion (formerly Brush); Stanford Materials, and The Low Hanging Fruit Co. BV.

Opportunities in Scandium

With a price of $1,500-$2,000 per kilogram being quoted for scandium oxide (99.9% purity) around the middle of this year, it is not surprising that a number of mining operations have actively been looking at the possibility of producing the metal.

In addition to China and Russia, resources of the metal stretch in a huge “S” from Australia in the south, through Madagascar, up through Kazakhstan and Ukraine, and ending in Norway in the north. Geographically, there certainly appears to be ample opportunities for mining exploration companies to convene a “scandium rush.”

It should be noted, however, that much of such optimism for scandium’s future among the interested mining community is based on a very short list of quite significant factors:

  1. The increased use of scandium alloys — particularly in the aero industry;
  2. The acceptance, and commercialization, of scandium-containing SOFCs;
  3. The rapid exhaustion of current scandium stockpiles; and,
  4. The superior economics of “primary” scandium extraction, albeit alongside that of both nickel and cobalt, for example, from mines, over those of its recovery from existing tailings.

Factor 3) will be dependent on both factors 1) and 2), and there is certainly enough doubt about both to continue to remain cautious. 

However, the attraction of such “primary” scandium extraction projects as proposed by the likes of either Australia’s Metallica Minerals (MLM:AU), with its NORNICO project in northern Queensland, or the joint venture between its Jervois Mining (JRV:AU), should be carefully considered in the context of just how much scandium is currently lying around globally.

And that is not even taking into account the possibility of extracting the metal from the “red mud” residues left over from using the Bayer process to produce aluminum.

Conclusion

Of all the minor/strategic metals, consumption of scandium, in whatever form, must be one of the smallest.  The market for the metal and its compounds is miniscule.

If, however, demand were to take off — both in aero industry and fuel cell usage — then the story could, rapidly, become very different.

For those wanting to keep a watching brief on the metal et al, keep up to date with who is developing what processes and where the metal and its compounds are being extracted from the copious amounts of scandium-tailings that are still lying untouched worldwide.

On the other hand, perhaps extracting the scandium from such tailings is a story very much in the same genre as that of extracting all the various precious metals from the tailings at Tsumeb in Namibia.  Maybe only time will actually tell.

 

Resources

The Low Hanging Fruit Company
United States Geological Service (USGS)

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