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Biotite Hornblende Granite

Not only is hornblende often found in granite, but also in syenite, gabbro, basalts, gneisses, schists, and a wide array of other rock types. The calcium-rich amphibole, which generally ranges in color from a pure green to greenish-black, usually develops as short, thick prismatic crystals. It may also occur, however, in granular or fibrous forms, sometimes in massive deposits. Also, a type of hornblende called edenite, in which iron oxides comprise less than 5 percent of the chemical makeup, appears in significantly lighter hues of gray or white. Of little practical use, hornblende has negligible commercial value.


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