Mica word meaning and definition

[noun] any of various minerals consisting of hydrous silicates of aluminum or potassium etc. that crystallize in forms that allow perfect cleavage into very thin leaves; used as dielectrics because of their resistance to electricity

\Mi"ca\, n. [L. mica crumb, grain, particle; cf. F. mica.] (Min.) The name of a group of minerals characterized by highly perfect cleavage, so that they readily separate into very thin leaves, more or less elastic. They differ widely in composition, and vary in color from pale brown or yellow to green or black. The transparent forms are used in lanterns, the doors of stoves, etc., being popularly called {isinglass}. Formerly called also {cat-silver}, and {glimmer}. Note: The important species of the mica group are: {muscovite}, common or potash mica, pale brown or green, often silvery, including {damourite} (also called {hydromica}); {biotite}, iron-magnesia mica, dark brown, green, or black; {lepidomelane}, iron, mica, black; {phlogopite}, magnesia mica, colorless, yellow, brown; {lepidolite}, lithia mica, rose-red, lilac. Mica (usually muscovite, also biotite) is an essential constituent of granite, gneiss, and mica slate; {biotite} is common in many eruptive rocks; {phlogopite} in crystalline limestone and serpentine. {Mica diorite} (Min.), an eruptive rock allied to diorite but containing mica (biotite) instead of hornblende. {Mica powder}, a kind of dynamite containing fine scales of mica. {Mica schist}, {Mica slate} (Geol.), a schistose rock, consisting of mica and quartz with, usually, some feldspar.

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