Mica refers to a group of phyllosilicates characterized by their layered structure. The main varieties are muscovite, colorless to silvery, and biotite, generally brown to black, as well as fuchsite, green due to its chromium content, and lepidolite, pink to lilac, rich in lithium. Micas exhibit perfect cleavage, allowing them to be separated into thin, flexible, and shiny sheets. They are found in many igneous and metamorphic rocks, including granites, pegmatites, and mica schists.