Source : Webster's Revised Unabridged Dictionary (1913)

Gadolinite \Gad"o*lin*ite\, n. [Named after Gadolin, a Russian
   chemist.] (Min.)
   A mineral of a nearly black color and vitreous luster, and
   consisting principally of the silicates of yttrium, cerium,
   and iron.

Source : WordNet®

gadolinite
     n : a mineral that is a source of rare earths; consists of
         silicates of iron and beryllium and cerium and yttrium
         and erbium [syn: {ytterbite}]