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Hornblende

Picture Gallery of Amphibole Minerals

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Hornblende is the most common amphibole; it is usually black, shiny and brittle. This specimen from the Sierra Nevada is about 8 cm across. (more below)
Hornblende
Photo (c) 2007 Andrew Alden, licensed to About.com (fair use policy)
A long, dark mineral with abundant cleavage faces in a granitic rock is hornblende more often than not. The chemical makeup of hornblende is quite variable, so its formula is ugly: (Ca,Na)2-3(Mg,Fe+2,Fe+3,Al)5(OH)2[(Si,Al)8O22].

Hornblende is usually black but can also be dark green or brown. It is a common primary mineral in granitic rocks and a common metamorphic mineral in gneiss and schist.

Other Primary Minerals

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