The Collaborative International Dictionary of English v.0.48:

Hornblende \Horn"blende`\, n. [G., fr. horn horn + blende
   blende.] (Min.)
   The common black, or dark green or brown, variety of
   amphibole. (See Amphibole.) It belongs to the aluminous
   division of the species, and is also characterized by its
   containing considerable iron. Also used as a general term to
   include the whole species.
   [1913 Webster]

   Hornblende schist (Geol.), a hornblende rock of schistose
      structure.
      [1913 Webster]