mica mineral similar to muscovite, a basic silicate of sodium and aluminum; a member of the common mica group. It was thought to be an uncommon mineral, but experiment and investigation have shown that it is widespread in metamorphic schists and phyllites, in gneisses, in quartz veins, and in fine-grained sediments. It seems probable that much paragonite has been mistaken for muscovite. Fine-grained paragonite, like muscovite, is called sericite, or white mica. For chemical formula and detailed physical properties, see mica (table).