Muscovite (also known as Common mica, Isinglass, or Potash mica) is a phyllosilicate mineral of aluminium an potassium with formula: KAl2(AlSi3O10)(F,OH)2. It has a highly perfect basal cleavage yielding remarkably thin laminae (sheets), which are often highly elastic. Sheets of muscovite 5 metres by 3 metres have been found in Nellore, India.