1. n. [Geology]

[Muscovite mica K2Al4(Si6Al2O20(OH,F)4]

A group of sheet silicates characterized by a platy appearance and basal cleavage most common in igneous and metamorphic rocks. Several clay minerals, such as chlorite and glauconite, are closely related to the mica group.

See: chlorite,  clay,  glauconite,  granite,  illite,  kaolinite,  metamorphic,  mineral,  rock,  silicate mineral