Samarskite

from WordNet (r) 3.0 (2006)

samarskite
    n 1: a complex black mineral occurring in pegmatites

from The Collaborative International Dictionary of English v.0.48

Samarskite \Sa*mar"skite\, a. [After Samarski, a Russian.]
   (Min.)
   A rare mineral having a velvet-black color and submetallic
   luster. It is a niobate of uranium, iron, and the yttrium and
   cerium metals.
   [1913 Webster]