Muscovite (also known as common mica, isinglass, or potash mica ) is a hydrated phyllosilicate of aluminium Al )2, or (KF)6(H2O yielding remarkably thin laminae (sheets) which are often highly elastic. Sheets of muscovite 5 meters × 3 meters (16.5 feet × 10 feet) have been found in Nellore
Muscovite has a Mohs hardness face, 4 perpendicular to the of 2.76–3. It can be colorless or tinted through grays , browns, or (rarely) violet, and can be transparent or translucent. It is anisotropic. Its crystal system is monoclinic. The green, chromium ; mariposite is also a chromium-rich type of muscovite.
Muscovite is the most common mica , pegmatites , and as a contact metamorphic rock or as a secondary mineral, feldspar, etc. It is characteristic of peraluminous rock , in which the content of aluminum is relatively high. In pegmatites, it is often found in immense sheets that are commercially valuable. Muscovite is in demand for the manufacture of fireproofing and insulating materials and to some extent as a lubricant.
The name muscovite comes from Muscovy-glass, a name given to the mineral in Elizabethan England due to its use in medieval Russia ) as a cheaper alternative to glass in windows. This usage became widely known in England during the sixteenth century with its first mention appearing in letters by George Turberville, the secretary of England's ambassador to the Muscovite, in 1568.