National Minerals Information Center

Mica Statistics and Information

The mica group represents 37 phyllosilicate minerals that have a layered or platy texture.  The commercially important micas are muscovite and phlogopite.  Layering in the univalent (potassium, sodium), or true, micas imparts perfect basal cleavage, allowing crystals to be split into very thin sheets that are tough and flexible.  Layering in the divalent, or brittle, micas also results in perfect basal cleavage; the greater bond strengths, however, make them more brittle and less flexible.  Mica sheets are also transparent to opaque, resilient, reflective, refractive, dielectric, chemically inert, insulating, lightweight, and hydrophilic.  Mica also is stable when exposed to electricity, light, moisture, and extreme temperatures.

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Kenneth Curry

USGS Mineral Commodity Specialist
Commodity Statistics and Information
Phone: 703-648-7793