Muscovite sheets 5 by 3 meters have been found at Nellore, India — among the largest crystal sheets of any mineral.
Known as 'Muscovy glass', it glazed windows in medieval Russia, and George Turberville mentioned it in 1568 letters as secretary to the ambassador to Ivan the Terrible.
Muscovite is in demand for fireproofing and insulating materials, and serves as a lubricant and filler in paints, plastics, wallboard, cosmetics and drilling mud.