The Collaborative International Dictionary of English v.0.48:

Tantalite \Tan"ta*lite\, n. [Cf. F. tantalite.] (Min.)
   A heavy mineral of an iron-black color and submetallic
   luster. It is essentially a tantalate of iron.
   [1913 Webster]

WordNet (r) 3.0 (2006):

tantalite
    n 1: a mineral consisting of tantalum oxide of iron and
         manganese that occurs with niobite or in coarse granite; an
         ore of tantalum