The Steenkampskraal mine north of Cape Town. Picture: Steenkampskraal mine website With the volatile geopolitics in the world currently experiences, there is talk about access to rare earth elements as much as there is about who has access to the most oil reserves. Why are these rare earth elements so important and does South Africa have any that could make it a target?
South Africa has two mines where rare earth elements are produced:Steenkampskraal Mozanite Mine, located 350km north of Cape TownandRainbow Rare Earths in Phalaborwa. We asked Graham Soden, director, CEO and mine manager of Steenkampskraal, what makes these elements so rare if they are not particularly rare in the earth’s crust. Soden says when rare earth elements were first discovered between the late 1700s and mid-1800s, they were found in unusual, “rare” minerals that were not common to miners and chemists of the time.
“These minerals, such as ytterbite, later renamed gadolinite, were chemically confusing and difficult to separate. Therefore, they were called “rare earths”, with the word “earths” referring to the old term for oxide minerals and “rare” used because the minerals were rare in commerce and discovery, not in actual abundance.” He points out that they are rarely found in economically viable concentrations. “Although elements, such as cerium and lanthanum are as abundant as copper or more, they are dispersed and not concentrated in ore-like deposits and chemically similar which means that they rarely separate naturally into rich pockets, making these deposits geologically rare.” This raises the question that if they are not rare, why are they so valuable today?
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Soden points out that abundance does not mean accessibility, while these elements also occur in very low ore grades. “Good deposits might only contain 3–15% monazite or bastnaesite and within that, only a few percent of the specific rare earth elements are desirable. “This means large volumes of run of mine needs to be produced and very large intricate processing plants are required.
Rare earths have nearly identical ionic sizes and very similar chemical behaviour. “Separating them into individual oxides or metals requires solvent extraction circuits with hundreds to thousands of stages, strong acids and bases and tight environmental controls that makes rare earth element production capital-intensive and technically demanding.”
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