Biotite

Biotite is a common Phyllosilicate Mineral that contains Potassium , Magnesium , Iron and Aluminium . It is sometimes called "iron mica" and is found in Granitic rocks, Gneiss es, and Schist s. Like other Mica minerals, biotite has a highly perfect basal cleavage, its flexible sheets easily flaking off. It has a Hardness of 2.5 - 3, a Specific Gravity of 2.7 - 3.1, is colored Green ish to Brown or Black , and can be transparent to opaque. Biotite is occasionally found in large sheets, especially in Pegmatite veins, and also occurs as a contact Metamorphic Rock or the product of the alteration of Hornblende , Augite , Wernerite , and similar minerals.

Biotite occurs in the Lava of Mount Vesuvius , at Monzoni , and many other Europe an locations. In the United States , it is found in the pegmatites of New England , Virginia and North Carolina , as well as in the granite of Pikes Peak , Colorado .

Biotite was named in honor of the French Physicist Jean-Baptiste Biot .

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