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PHLOGOPITE

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Originally appearing in Volume V21, Page 447 of the 1911 Encyclopedia Britannica.
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PHLOGOPITE , a See also:

mineral belonging to the See also:group of micas (q.v.). It is a See also:magnesium See also:mica, differing from See also:biotite in containing only a little See also:iron; the chemical See also:formula is [H,K,(MgF)]3Mg3Al(SiOi)3. It crystallizes in the See also:monoclinic See also:system, but the crystals are roughly See also:developed. There is a perfect cleavage parallel to the basal See also:plane; the cleavage flakes are not quite so elastic as those of See also:muscovite. Sometimes it is quite colourless and transparent, but usually of a characteristic yellowish-See also:brown See also:colour, and often with a silvery lustre on the cleavage surfaces, hence the See also:trade name " See also:silver See also:amber mica " for some varieties. The name phlogopite is from Gr. 4 Xoynnros (fiery-looking), the mineral being sometimes brownish-red and coppery in See also:appearance. The hardness is 22-3, and the specific gravity 2.78-2.85. The optic axial plane is parallel to the plane of symmetry and the axial See also:angle o°-lo°. Phlogopite occurs chiefly as scales and plates embedded in crystalline limestones of the Archean formation. The mica See also:mined in See also:Canada and See also:Ceylon is mainly phlogopite; and is largely used as an insulator for See also:electrical purposes. In Canada it occurs with See also:apatite in See also:pyroxene rocks which are intrusive in Laurentian gneisses and crystalline limestones, the See also:principal See also:mining See also:district being in See also:Ottawa See also:county in See also:Quebec and near See also:Burgess in See also:Lanark county, See also:Ontario.

In Ceylon, the mineral forms irregular See also:

veins, rarely exceeding one or two feet in width, traversing See also:granulite, especially near the coptact of this See also:rock with crystalline See also:limestone. (L. J.

End of Article: PHLOGOPITE

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PHLOX (Nat. Ord. Polemoniaceae)

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