'Fergusonite' definitions:

Definition of 'fergusonite'

(from WordNet)
noun
A dark mineral consisting of oxides of yttrium and erbium and tantalum and other minerals

Definition of 'Fergusonite'

From: GCIDE
  • Fergusonite \Fer"gu*son*ite\, n. (Min.) A mineral of a brownish black color, essentially a tantalo-niobate of yttrium, erbium, and cerium; -- so called after Robert Ferguson. [1913 Webster]