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biotite
biotite An important rock-forming silicate mineral; a member of the mica group K2(Mg,Fe)6[Si3AlO10]2(OH,F)4, in which the Mg/Fe ratio is less than 2:1; biotite forms a series with phlogopite (of similar composition, but with Mg/Fe greater than 2:1) and may have Fe3+, Ti4+, and Al3+ also present in the formula; sp. gr. 2.7–3.3; hardness 2–3; monoclinic; black, dark brown, or greenish-black; vitreous to sub-metallic lustre; crystals tabular and pseudo-hexagonal, with lamellar aggregates and flakes; cleavage perfect basal mica; occurs in granites, syenites, and diorites, in schists and gneisses, in contact metamorphic rocks, and often in sedimentary rocks.
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AILSA ALLABY and MICHAEL ALLABY. "biotite." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>. AILSA ALLABY and MICHAEL ALLABY. "biotite." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1O13-biotite.html AILSA ALLABY and MICHAEL ALLABY. "biotite." A Dictionary of Earth Sciences. 1999. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O13-biotite.html |
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biotite
biotite , iron-rich variety of phlogopite, most abdunant of the mica minerals. |
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Cite this article
"biotite." The Columbia Encyclopedia, 6th ed.. 2008. Encyclopedia.com. 10 Feb. 2012 <http://www.encyclopedia.com>. "biotite." The Columbia Encyclopedia, 6th ed.. 2008. Encyclopedia.com. (February 10, 2012). http://www.encyclopedia.com/doc/1E1-biotite.html "biotite." The Columbia Encyclopedia, 6th ed.. 2008. Retrieved February 10, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-biotite.html |
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