Many types of Mica
There are many types of mica, but only six or so are common rock-forming minerals. Mica capacitors are normally made from muscovite mica, or potassium aluminum silicate, KAl2Si3O10(OH)2 . It is thermally stable up to 500°C, and has a high dielectric strength. Phlogopite mica, or potassium magnesium silicate, KMg3Si3AlO10(OH)2 , is softer than muscovite mica and has less desirable electrical characteristics, but it may be used up to 900°C. Mica deposits are found in Madagascar, Central Africa, South America, and India. India is probably the biggest supplier of mica.
