About Mica

The mica group of sheet silicate (phyllosilicate) minerals includes several closely related materials having close to perfect basal cleavage. All are monoclinic, with a tendency towards pseudohexagonal crystals, and are similar in chemical composition. The nearly perfect cleavage, which is the most prominent characteristic of mica, is explained by the hexagonal sheet-like arrangement of its atoms. The word ''mica'' is derived from the Latin word mica, meaning ''a crumb'', and probably influenced by micare, ''to glitter''. Chemically, micas can be given the general formula Structurally, micas can be classed as dioctahedral (Y = 4) and trioctahedral (Y = 6). If the X ion is K or Na, the mica is a ''common'' mica, whereas if the X ion is Ca, the mica is classed as a ''brittle'' mica. Common...'

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