A rare earth mineral, also known as Rare Earth Metals and Rare Earth Elements, are a total of 17 chemical elements consisting of the 15 lanthanides (ln) and scandium (Sc) and yttrium (y). The first rare earth minerals were found in the 18th century in the town of Ytterby, Sweden. Yttrium and many other of the elements having names derived from the area.
Rare earth minerals are usually found in association with alkaline to peralkaline igneous complexes, in pegmatites associated with alkaline magmas and in or associated with carbonatite intrusives. Perovskite mineral phases are common hosts to rare earth elements within the alkaline complexes. Mantle-derived carbonate melts are also carriers of the rare earths. Hydrothermal deposits associated with alkaline magmatism contain a variety of rare earth minerals.
Rare earth metals are not as rare as their name suggests. Some are amongst the most abundant elements in the Earth’s crust, with cerium being the 25th most abundant element, although promethium is extremely rare as it is estimated that only half a kilogram of the mineral is found in the entire Earth’s crust.
The reason they are referred to as rare, is that unlike other minerals which are mined, rare earth minerals are found in extremely low densities rather than exploitable geographical seems. As a result mining rare earths is more difficult and expensive to exploit.
The following includes the relatively common hydrothermal rare earth minerals and minerals that often contain significant rare earth substitution: