Micas | Article about Micas by The Free Dictionary
mica (mī`kə), general term for a large group of minerals, hydrous silicates of aluminum and potassium, often containing magnesium, ferrous iron, ferric iron, sodium, and lithium and more rarely containing barium, chromium, and crystallize in the monoclinic system, but mica is most commonly found in the form of scales and sheets. All the micas have an excellent basal cleavage ...