Lanthanum - Occurrence

Occurrence

Although lanthanum belongs to the element group called rare earth metals, it is not rare at all. Lanthanum is available in relatively large quantities (32 ppm in Earth’s crust). "Rare earths" got their name because they were indeed rare as compared to the "common" earths such as lime or magnesia, and historically only a few deposits were known. Lanthanum is taken into consideration as a rare earth metal because the process to mine is difficult, time consuming and expensive.

Monazite (Ce, La, Th, Nd, Y)PO₄, and bastnäsite (Ce, La, Y)CO₃F, are the principal ores in which lanthanum occurs, in percentages of up to 25 to 38 percent of the total lanthanide content. In general, there is more lanthanum in bastnäsite than in monazite. Until 1949, bastnäsite was a rare and obscure mineral, not even remotely contemplated as a potential commercial source for lanthanides. In that year, the large deposit at the Mountain Pass rare earth mine in California was discovered. This discovery alerted geologists to the existence of a new class of rare earth deposit, the rare-earth bearing carbonatite, other examples of which soon surfaced, particularly in Africa and China.