Definitions for "Fergusonite"
A mineral of a brownish black color, essentially a tantalo-niobate of yttrium, erbium, and cerium; -- so called after Robert Ferguson.
a dark mineral consisting of oxides of yttrium and erbium and tantalum and other minerals
Fergusonite is a mineral comprising a complex oxide of various rare earth elements. Its formula is given basically as (Ce,La,Nd)NbO4. However other analyses also include yttrium, erbium, and tantalum.