Biotite: a mineral belonging to the Miche Group, meeting the formula K(Mg,Fe)3 [(OH,F)2 AlSi3O10]. Translucent to opaque, with glassy to nacreous to metallic luster, and dark brown to dark green to black color. It crystallizes in the Monoclinic System and occurs in tabular crystals with vaguely hexagonal outline, as well as in aggregates with lamellar, foliated, sometimes granular-opaque appearance. It is a component of magmatic and metamorphic rocks.
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IGR – Rivista Italiana di Gemmologia, the Italian Gemological Review, is the leading International Gemological Magazine in Italy masterminded by Gem-Tech Gemological Institute, a broad information framework for Gemologists as well as professionals involved daily in the gemstone business.
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