sodalite

from WordNet (r) 3.0 (2006)

sodalite
    n 1: a vitreous mineral consisting of sodium aluminum silicate
         and sodium chloride in crystalline form; occurs in igneous
         rocks

from The Collaborative International Dictionary of English v.0.48

Sodalite \So"da*lite\, n. [Soda + -lite: cf. F. sodalithe.]
   (Min.)
   A mineral of a white to blue or gray color, occuring commonly
   in dodecahedrons, also massive. It is a silicate of alumina
   and soda with some chlorine.
   [1913 Webster]