rare earth

(This etymology is missing or incomplete. Please add to it, or discuss it at the Etymology scriptorium. Particularly: “When did the term start to be used?”)

rare earth (plural rare earths)

1. (chemistry) Any 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.
2. a rare earth element

• rare earth element
• rare earth metal
• rare earth mineral

• rare-earth element on Wikipedia.Wikipedia
• “rare earth”, in Lexico, Dictionary.com; Oxford University Press, 2019–2022.