Mica is a group of silicate minerals that are physically and chemically similar to one another. There are 37 known mica minerals, including biotite, lepidolite, muscovite and phlogopite. Mica minerals form in sedimentary, igneous and metamorphic rock formations in layers. Found as sheets, flakes and crystals, mica minerals are lightweight, soft, flexible, heat resistant and do not conduct electricity. These properties lead to many mica minerals being used in the electronics and electrical industries.
Mica minerals, especially those found in sheet form, are pliable and tolerant to being machined into any form necessary for electrical and electronic components. Mica minerals in sheet form can be split to thicknesses of 0.125 millimeters or thinner while maintaining their electrical and heat-resistant properties. Muscovite is the principal mineral used in high-frequency and radio-frequency capacitors. Mica sheets are found in radiation detectors, high-pressure boilers and advanced aerospace applications.
Mica minerals were also used in ancient times by various civilizations, some of which predate recorded history. Mica minerals were sometimes used to create white pigments for cave paintings dating as far back as the Upper Paleolithic period. Pottery made by the Tewa Pueblo tribe is coated with ground mica minerals to create dense, glittering finishes.