apatite

from WordNet (r) 3.0 (2006)

apatite
    n 1: a common complex mineral consisting of calcium fluoride
         phosphate or calcium chloride phosphate; a source of
         phosphorus

from The Collaborative International Dictionary of English v.0.48

Apatite \Ap"a*tite\, n. [Gr. ? deceit, fr. ? to deceive; it
   having been often mistaken for other minerals.] (Min.)
   Native phosphate of lime, occurring usually in six-sided
   prisms, color often pale green, transparent or translucent.
   [1913 Webster]