page_title: Muscovite
hierarchical_section_title: Muscovite
caption_attribution_description: English: Beryl (Var.: Morganite), Muscovite Locality: Paprok, Nuristan Province (Nurestan; Nooristan), Afghanistan (Locality at mindat.org) Size: 5.9 x 4.8 x 3.4 cm. This is a pristine 2-cm crystal of pink morganite , with sharp faces and windows on the sides into the gemmy 100% clean interior. It is nestled in a bed of bladed muscovite. Ex. Marty Zinn Collection. Deutsch: Beryll (Var.: Morganit), Muskovit Fundort: Paprok, Nuristan, Afghanistan (Fundort bei mindat.org) Größe: 5.9 x 4.8 x 3.4 cm.
context_page_description: Muscovite is a hydrated phyllosilicate mineral of aluminium and potassium with formula KAl₂(F, OH)₂, or (KF)₂(Al₂O₃)₃(SiO₂)₆. It has a highly perfect basal cleavage yielding remarkably thin laminae which are often highly elastic. Sheets of muscovite 5 meters × 3 meters have been found in Nellore, India.
  Muscovite has a Mohs hardness of 2–2.25 parallel to the [001] face, 4 perpendicular to the [001] and a specific gravity of 2.76–3. It can be colorless or tinted through grays, browns, greens, yellows, or violet or red, and can be transparent or translucent. It is anisotropic and has high birefringence. Its crystal system is monoclinic. The green, chromium-rich variety is called fuchsite; mariposite is also a chromium-rich type of muscovite.
  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. 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.
context_section_description: Muscovite (also known as common mica, isinglass, or potash mica) is a hydrated 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 laminae (sheets) which are often highly elastic. Sheets of muscovite 5 meters × 3 meters (16.5 feet × 10 feet) have been found in Nellore, India. 
   
  Muscovite has a Mohs hardness of 2–2.25 parallel to the [001] face, 4 perpendicular to the [001] 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.  It is anisotropic and has high birefringence.  Its crystal system is monoclinic. The green, chromium-rich variety is called fuchsite; mariposite is also a chromium-rich type of muscovite.
  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.  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 (Muscovy) 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 tsar Ivan the Terrible, in 1568.
caption: Muscovite with beryl (var. morganite) from Paprok, Afghanistan
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