Cassiterite

from WordNet (r) 3.0 (2006)

cassiterite
    n 1: a hard heavy dark mineral that is the chief source of tin

from The Collaborative International Dictionary of English v.0.48

Cassiterite \Cas*sit"er*ite\, n. [Gr. ? tin.] (Min.)
   Native tin dioxide; tin stone; a mineral occurring in
   tetragonal crystals of reddish brown color, and brilliant
   adamantine luster; also massive, sometimes in compact forms
   with concentric fibrous structure resembling wood ({wood
   tin}), also in rolled fragments or pebbly ({Stream tin}). It
   is the chief source of metallic tin. See {Black tin}, under
   {Black}.
   [1913 Webster]