biotite

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biotite

(bī`ətīt'), iron-rich variety of phlogopite, most abdunant of the micamica
, general term for a large group of minerals, hydrous silicates of aluminum and potassium, often containing magnesium, ferrous iron, ferric iron, sodium, and lithium and more rarely containing barium, chromium, and fluorine.
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 minerals.

Biotite

 

(after the French scientist J. B. Biot, 1774–1862), a mineral of the mica group. Biotite is structurally related to the micaceous aluminosilicates. Its chemical formula is K(Mg, Fe)3AlSi3O10(OH,F)2. The color of the thin sheets is from blackish-brown to brownish-green. Biotite occurs widely as a rock-forming mineral in igneous and metamorphic rocks. The largest biotite crystals, reaching 1–1.5 m, are found in pegmatite veins. Biotite is used in light-duty electrical insulating articles, and its powder is used in the preparation of bronze paint.,

biotite

[′bī·ə‚tīt]
(mineralogy)
A black, brown, or dark green, abundant and widely distributed species of rock-forming mineral in the mica group; its chemical composition is variable: K2[Fe(II),Mg]6-4[Fe(III),Al,Ti]0-2(Si6-5,Al2-3)O20-22(OH,F)4-2. Also known as black mica; iron mica; magnesia mica; magnesium-iron mica.
References in periodicals archive ?
The Novosibirsk massif is composed of porphyritic biotite granites, granosyenites and biotite-containing leucogranites (Mochishche stock).
The main area of the massifs is mediumgrained biotite leucogranites.
In addition, Figures 4 and 5, and the log f[O.sub.2]-T diagram for biotites (Figure 6) at [P.sub.H20] = 207.0 MPa (Wones and Eugster, 1965), suggest that these biotites were crystallized at log f[O.sub.2] values between-11.6 and-12.5.
However, the biotites within the Wushan granodiorite are unaltered (Figure 2), and Etsuo et al.
Gilkes RJ, Suddhiprakarn A (1979) Biotite alteration in deeply weathered granite.
5b; Vernon 1986) defined by minute, oriented euhedral biotite inclusions (Mg/(Mg+Fe) atomic ratio (Mg#)--0.55; Rb/Sr = 162-244).
Matejovska, O.: 1970, Composition of coexisting garnets and biotites from some granulites of Moldanubicum, Czechoslovakia, N.
Biotite in this study refers to a regular 1:1 interstratified (mixed-layer) biotite-vermiculite, a mineral recognized in many vermiculite deposits (Boettcher, 1966).
The smallest effect of heterogeneities is observed in the samples of biotite (h003), garnet (h014) and mineralized chloritized garnet amphibolite (h028) with a fairly strict one-way orientation of crystalline-acoustic axes in mineral grains.
Subhedral grains of biotite, plagioclase and euhedral grains of zircon are enclosed in bigger quartz grains.
Adopted nomenclature differentiates phlogopite from biotite on the basis of the Mg:Fe molar proportions: phlogopite (>2:1) and biotite (<2:1).