Real Dictionary

mica
variable noun: Mica is a hard mineral which is found as small flat crystals in rocks. It has a great resistance to heat and electricity.

mica in American English
any of a group of minerals that are complex silicates that crystallize in thin, somewhat flexible, translucent or colored, easily separated layers, including muscovite, biotite, and lepidolite: mica is resistant to heat and electricity
noun: any member of a group of minerals, hydrous silicates of aluminum with other bases, chiefly potassium, magnesium, iron, and lithium, that separate readily into thin, tough, often transparent, and usually elastic laminae; isinglass

mica in British English
noun: any of a group of lustrous rock-forming minerals consisting of hydrous silicates of aluminium, potassium, etc, in monoclinic crystalline form, occurring in igneous and metamorphic rock. Because of their resistance to electricity and heat they are used as