Abundant silicate mineral that contains potassium and aluminum and has a layered atomic structure. It is the most common member of the mica group. Because it occurs in thin, transparent sheets, it was used in Russia for window panes and became known as Muscovy glass (isinglass), hence its name. Muscovite is usually colourless but may be light gray, brown, pale green, or rose red. Its low iron content makes it a good electrical and thermal insulator.
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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 metres by 3 metres have been found in Nellore, India.
Muscovite melts at approximately 1320 °C, has a Mohs hardness of 2–2.25 parallel to the  face, 4 perpendicular to the  and a specific gravity of 2.76–3. It can be colorless or tinted through grays, browns, greens, yellows, or (rarely) violet or red, and can be transparent or translucent. The green, chromium-rich variety is called fuchsite.
Muscovite is the most common mica, found in granites, pegmatites, gneisses, and schists, and as a contact metamorphic rock or as a secondary mineral resulting from the alteration of topaz, feldspar, kyanite, etc. 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 of muscovite comes from Muscovy-glass, a name formerly used for the mineral because of its use in Russia for windows. It is anisotropic and has high birefringence. Its crystal system is monoclinic.
Provenance of detrital muscovite in Cambrian Avalonia of Maritime Canada: [sup.40]Ar/ [sup.39]Ar ages and chemical compositions.(Report)
Mar 01, 2009; Introduction For many years, U-Pb ages of detrital zircon grains have been used to infer the provenance of sedimentary units....
Recrystallization or Cooling Ages: In Situ UV-Laser ^Sup 40^ar/ ^sup 39^ar Geochronology of Muscovite in Mylonitic Rocks
Jul 01, 2004; Abstract: The intra-grain ^sup 40^Ar/^sup 39^Ar age distributions of muscovite from grecnschist-facies mylonite zones are...