hornblende (n.)

common dark mineral, 1770, from German Hornblende, from horn "horn of an animal" (see horn (n.)) + blende (see blende).

The term "Hornblende" is an old German name for any dark, prismatic crystal found with metallic ores but containing no valuable metal (the word "Blende" indicates "a deceiver") [Herbert Bucksch, "Dictionary Geotechnical Engineering," 1995]

Related: Horneblendic.