Mica is found in nature in the form of crystals. It occurs as seams in hard rock, usually pegmatite or granite. Mica is a hydrated alumina-silicate. Compound of Iron, sodium, potassium, etc may also be present in Mica. Mica is found in two types. The most important forms are MUSCOVITE and other is a PHLOGOPITE. Muscovite is a colorless, but also has Ruby, Green or other tints. Phlogopite usually has a very dark color from amber, gold and brown to almost black, though it sometimes occurs in very light colors also. The electrical properties of Muscovite, which is one of the best insulating materials, are superior to those of phlogopite, and in addition it is somewhat stronger mechanically and is harder and more flexible. The Phlogopite is softer than Muscovite and has poorer electrical properties and electrical resistance.
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Processing :-

The ordinary mica crystals as they come out of a mine is in form of rough books or lumps of irregular shape, size and thickness, associated with impurities and structural imperfections. They have to undergo a long operation of cutting, sorting and processing from crude to commercial quality. No machine has yet been designed to process mica mechanically.The operations performed consists of cobbling or cleaning the crude crystals as extracted from the mine with its associated impurities; rifting or splitting the cobbled mica into usable sheets by sickle and then by sharp knife removing major flaws and structural imperfections, such as cracks, holes, reeves, cross grains and other physical defects to obtain the maximum usable area with minimum wastage. The trimming of mica is a skilled hand-operation in which cracks and imperfections are removed at the edges of the sheets using a knife while saving the best area of usable sheet. The knife-dressed sheet mica of irregular polygonal shapes is finally graded into different standard sizes and commercial qualities before they are offered for marketing.
View flowchart of Mica processing