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]
A common, green to black mineral of the amphibole group. It has a variable composition and occurs in monoclinic crystals with a hexagonal cross-section, in fibrous forms, or in granular forms. Hornblende is found in many metamorphic and igneous rocks. Chemical formula: (Ca,Na)2-3(Mg,Fe,Al)5(Al,Si)8O22(OH)22.