The global transition to renewable energy infrastructure is driving rapid growth in the demand for critical raw materials), including rare earths, gallium, germanium, cobalt, nickel and many other elements.
One challenge with these critical materials is their key components often do not form their own mineral hosts. Instead, they occur as trace elements within other minerals making identification of the host-phase challenging. Identifying and concentrating these minerals can be as difficult as “finding a needle in a haystack”, following the old English proverb.
A good example is the rare earth elements can form carbonate and phosphate minerals but typically are found in minerals such as monazite (a phosphate), eudialyte (a complex silicate) or clay minerals in weathered deposits.
Another example is the production of the important elements gallium, germanium and indium for the electronics industry. Gallium has similar chemistry to aluminium and present in trace amounts in some bauxites. More commonly, all three elements tend to be enriched in higher abundance in sulfide ores, where they are hosted within minerals such as chalcopyrite and sphalerite as trace components.
Separation and concentration of these minerals are focused on the host-phase rather than the target elements. To aid successful separation, substantial mineralogical information is essential. Advanced mineralogical analyses are used to characterise critical metal mineralogy and inform process flowsheets, supporting the optimisation of target mineral separation and concentration.
Figure 1 shows a thin section of ion-adsorption clay ore showing up to 200 ppm Nd and 60 ppm Pr associated with opaque iron-rich phases. Goiás State, Brazil.
Figure 2 shows a Söhngeite (Ga(OH)3). Named in 1965 in honor of Gerhard Söhnge, former Chief Geologist of the Tsumeb Corporation, Namibia, and professor at Stellenbosch University. One of the few known Ga minerals, it is extremely rare and found only from its type locality.
