cryolite

from WordNet (r) 3.0 (2006)

cryolite
    n 1: a white mineral consisting of fluorides of aluminum and
         sodium; a source of fluorine [syn: {cryolite}, {Greenland
         spar}]

from The Collaborative International Dictionary of English v.0.48

Cryolite \Cry"o*lite\ (kr[imac]"?-l?t), n. [Gr. kry`os icy cold,
   frost + -lite: cf. F. cryolithe.] (Min.)
   A fluoride of sodium and aluminum, found in Greenland, in
   white cleavable masses; -- used as a source of soda and
   alumina.
   [1913 Webster]