Mineralogy and Crystallography

A Dictionary of Earth Sciences The Columbia Encyclopedia, 6th ed. Further reading

biotite

A Dictionary of Earth Sciences | 1999 | | Copyright

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>.

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biotite

The Columbia Encyclopedia, 6th ed. | 2008 | Copyright

biotite , iron-rich variety of phlogopite, most abdunant of the mica minerals.

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"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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