Mica is the name of a group of 37 phyllosilicate minerals with layered or lamellar texture. Mica is widely distributed and found in igneous, metamorphic and sedimentary regimes. Large crystals of mica used for various purposes are usually extracted from granite pegmatites. Commercially important micas are muscovite and phlogopite, which are used in various fields. The value of mica is based on several of its unique physical properties. The mica crystal structure forms layers that can be split or laminated into thin sheets, usually causing lamination in the rocks. These sheets are chemically inert, dielectric, elastic, flexible, hydrophilic, insulating, light, plastic, reflective, refracting, resilient and have opacity from transparent to opaque. Mica is stable when exposed to electricity, light, moisture and extreme temperatures. It has excellent electrical properties as an insulator and dielectric and can maintain an electrostatic field while dissipating minimal energy in the form of heat; it can be very thin while maintaining its electrical properties, has a high dielectric breakdown, thermally stable to 500 ° C and resistant to corona discharge. Muscovite, the main mica used in the electrical industry, is used in capacitors that are ideally suited for high frequencies and radio frequencies. Mica dust in the workplace is regarded as a hazardous substance for respiratory exposure above certain concentrations.