mica - any of various minerals consisting of hydrous silicates of aluminum or potassium etc. that crystallize in forms that allow perfect cleavage into very thin leaves; used as dielectrics because of their resistance to electricitymineral - solid homogeneous inorganic substances occurring in nature having a definite chemical composition biotite - dark brown to black mica found in igneous and metamorphic rock lepidolite - a mineral of the mica group; an important source of lithium muscovite - a colorless or pale brown mica with potassium paragonite - a colorless or pale brown mica with sodium phlogopite - a brown form of mica consisting of hydrous silicate of potassium and magnesium and aluminum |