Source : Webster's Revised Unabridged Dictionary (1913)

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.

Source : WordNet®

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