The word "mica" is thought to be derived from the Latin word micare, meaning to shine, in reference to the brilliant appearance of this mineral (especially when in small scales).
The mica group of sheet sillicate minerals includes several closely related materials having highly perfect basal cleavage.Micas are significant rock forming minerals being found in all three rock types: igneous, metamorphic and sedimentary. Because thin flakes of mica are generally flexible and brittle, it is surprising how resistant and durable mica crystals can be in withstanding high temperatures and pressures in metamorphic regimes as well as the punishment of erosional environments. The term "mica" is so familiar to the general public that it is often considered a mineral in itself. Of course it is actually a group of minerals and most people who are knowledgeable about minerals know the three most common mica minerals: muscovite, biotite, and lepidolite and perhaps a few of the less common micas glauconite, paragonite, phlogopite and zinnwaldite.
Chemical composition of some of the mica varieties:
Mica (muscovite in particular) has a wide variety of uses as an insulating material in electrical equipment due to its strongly dielectric properties and to its good electrical resistivity and capacitance stability. Mica also has a low coefficient of expansion, and it has been used extensively because of its heat resisting properties. Mica is used extensively in paints to increase weatherability and to reduce running, it is also used in the manufacture of wallpapers to give them a silky or shiny luster. Mica is also used in the manufacture of lubricants and in dry-powder fire extinguishers.