argentite

from WordNet (r) 3.0 (2006)

argentite
    n 1: a valuable silver ore consisting of silver sulfide (Ag2S)

from The Collaborative International Dictionary of English v.0.48

Argentite \Ar"gen*tite\, n. [L. argentum silver.] (Min.)
   Sulphide of silver; -- also called {vitreous silver}, or
   {silver glance}. It has a metallic luster, a lead-gray color,
   and is sectile like lead.
   [1913 Webster]