Phlogopite


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Related to Phlogopite: biotite

phlogopite

[′fläg·ə‚pīt]
(mineralogy)
K2[Mg,Fe(II)]6(Si6,Al2)O20(OH)4 A yellow-brown to copper mineral of the mica group occurring in disseminated flakes, foliated masses, or large crystals; hardness is 2.5-3.0 on Mohs scale, and specific gravity is 2.8-3.0. Also known as bronze mica; brown mica.

Phlogopite

 

a mineral of the phyllosilicate class; an iron-poor magnesium mica (Mg/Fe > 2) of the isomorphic biotite-phlogo-pite series. Phlogopite has a chemical composition of K(Mg, Fe)3[AlSi3O10](OH, F)2. Impurities include Na2O (up to 8 percent), TiO2 (up to 9 percent), and MnO (up to 18 percent; such phlogopite is called manganophyllite), as well as rubidium, cesium, and barium. In man-made fluorphlogopite, all the (OH) is substituted by fluorite.

Phlogopite crystallizes in the monoclinic system, forming pseu-dohexagonal tabular, prismatic, or other types of crystals, which reach 2 m in length; it also forms foliated or scaly aggregates. Iron-free phlogopites are colorless, while ferruginous phlogopites are green and brown and have a characteristic reddish tint. Phlogopite has perfect cleavage and splits easily into flexible sheets. It has a hardness of 2–2.5 on Mohs’ scale and a density of 2,700–2,850 kg/m3. It is a good dielectric.

Phlogopite is widely distributed in metamorphic rocks and upon weathering alters to vermiculite. Industrially useful deposits occur as a result of metasomatism at the contact zone of magnesium rocks (dolomites, hyperbasic rocks) and aluminosilicate rocks (gneisses, pegmatites, alkali magmatites).

Because of its excellent electrical insulating properties, phlogopite is used in electrical technology. In this case, the value of the raw material is determined by the size of defect-free crystals. Phlogopite is partially replaced by synthetic fluorphlogopite, crystallized from a melt.

The USSR has the largest phlogopite province in the world at Aldan (the Emel’dzhak, Timpton, Kuranakh, and other deposits), as well as deposits on the Kola Peninsula (Kovdor and others), in the Transbaikal Region (Sliudianka), and elsewhere. Phlogopite is also found on Madagascar and in Canada, Sri Lanka, India, and North Korea.

REFERENCES

Litsarev, M. A. Genezis flogopitovykh mestorozhdenii Aldana. Moscow, 1961.
Ternovoi, V. I., B. V. Afanas’ev, and B. I. Sulimov. “Geologicheskoe stroenie i usloviia obrazovaniia Kovdorskogo mestorozhde-niia flogopita.” Sovetskaia geologiia, 1967, no. 2.

P. P. SMOLIN

References in periodicals archive ?
This pressure was confirmed by the consideration of the phlogopite component in biotite and, thus, the possibility to calculate IP1.
On a decouvert que les gisements d'emeraude et autres beryls verts sont localises dans la zone de contact separant une zone de schistes a phlogopite et de veines intrusives de quartz, d'une zone de pegmatites.
The presence, at vein margins, of pure [V.sub.2][O.sub.3] (the rare mineral karelianite) and vanadian phlogopite with a [V.sub.2][O.sub.3] content between 4 and 11 weight percent has been taken as evidence of a high vanadium content in the original sediments.
Un echantillon du granite de Baring a ete situe a 421,1 [+ or -] 0,8 Ma par cristallisation au u-Pb (a partir du zircon) et une datation de la phlogopite de l'unite de gabbro a olivine du gabbro de St.
Hornblende and phlogopite ages from the host rocks of the pluton (both the Green Head Group and the Brookville Gneiss) show similar ages (Fig.
Phlogopite K[Mg.sub.3][Si.sub.3]Al[O.sub.10](F,OH)[.sub.2]
Premium grades of highly pure, low-iron, platy tales, high-purity calcium carbonates, phlogopite micas, and ground white barium sulfate for high-density compounds.
This glass locally contains corroded primary spinel and phlogopite. 3) Silica-undersaturated glass in partly to completely broken down amphibole grains in clinopyroxenites.
% (as the amount of Mg is prevailing over Fe, the chemical composition is closer to phlogopite than to biotite) and CaO values varying from 0.20 to 0.22 wt.
Associated species reported include fluorite, datolite, quartz, barite, chabazite, calcite, pyroxene, phlogopite, pyrite and pyrrhotite.
Siliceous marble contains more than 20% calcite and a variety of metamorphic minerals including phlogopite, tremolite/actinolite, and graphite.
The An Phu mine near An Phu village in the Luc Yen mining district, Vietnam has been the source of attractive specimens of ruby corundum and large purple to red spinel crystals, as well as phlogopite, pyrite, dravite and green edenite crystals embedded in white marble matrix.