About Hornblende

Hornblende is a complex inosilicate series of minerals (ferrohornblende a__ magnesiohornblende). 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 is an isomorphous mixture of three molecules; a calcium-iron-magnesium silicate, an aluminium-iron-magnesium silicate, and an iron-magnesium silicate. The general formula can be given as (Ca,Na)2a__3(Mg,Fe,Al)5(Al,Si)8O22(OH,F)2. Some metals vary in their occurrence and magnitude: Hornblende has a hardness of 5a__6, a specific gravity of 2.9a__3.4 and is typically an opaque green, greenish-brown, brown or black color. Its cleavage angles are at 56 and 124 degrees. It is most often confused with the minerals augite and biotite mica, both of which are black and...'

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