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.

 

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