Muscovite (also known as common mica, isinglass, or potash mica) is a phyllosilicate mineral of aluminium and potassium with formula KAl₂(AlSi₃O₁₀)(F,OH)₂, or (KF)₂(Al₂O₃)₃(SiO₂)₆(H₂O). It has a highly perfect basal cleavage yielding remarkably thin laminæ (sheets) which are often highly elastic. Sheets of muscovite 5 m × 3 m have been found in Nellore, India.