rare earth

rare earthnoun

• 1

  chemistrynatural-sciencesphysical-sciencesAny of the naturally occurring oxides of the lanthanide metals; they are widely distributed in relatively small concentrations and are used in glassmaking, ceramic glazes etc.

  • Meronyms: rare earth element, rare earth metal
  • The metallic base of yttria, a very rare earth, discovered in a mineral called godolinite.
• 2

  A rare earth element.

  • Near-synonym: lanthanide
  • Despite their name, rare earths are not so rare. The most common, cerium, is as plentiful in the Earth's crust as copper or lead. The difference between them and more familiar materials is that, in nature, rare earths are almost never found on their own. Rather, they're mixed with other minerals, and often at low concentrations, making them difficult to mine economically.