Question

why are the lanthanides called the rare earth metals , even though they are not rare in
the earth's crust ( got this doubt while reading a book for competitive exam book ) .

Answer 1

Lanthanides are known as rare earth as they are rarely found in sufficient abundance in a single location, and they are dispersed. Their ore deposits are not economically available. Due to this there is scarcity of these mineral deposits in earth. Hence they are called by the term "rare earth".