Hornblende
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Hornblende is a complex inosilicate series of minerals. It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole. Hornblende minerals are common in igneous and metamorphic... Wikipedia
Cleavage: Imperfect at 56° and 124°
Category: Silicate mineral
Color: Black to dark green or brown
Crystal habit: Hexagonal/granular
Crystal system: Monoclinic
Formula (repeating unit): Ca2(Mg,Fe,Al)5(Al,Si)8O22(OH)2
Fracture: Uneven