Mineral description : Muscovite

Triangular muscovite crystal from Varuträsk.
Muscovite aggregate with schoerl from Kaatiala, Finland.
Muscovite crystals as fivepointed stars, unknown locality.
Muscovite crystal from Ytterklippen.
Muscovite as small balls from Kaatiala, Finland.
This is a sign of beryl in the vincinity.

Mineral class Silicates : Phyllosilicates : Mica group.
Chemical formula KAl2(AlSi3O10)(F,OH)2
Crystal system Monoclinic
Habitus Tabular flat crystals with six sided to triangular cross section. Twinning may produce fivepointed stars sometimes. Commonly as foliated lamellar masses. Also as fine grained masses.
Cleavage Perfect basally, uneven fracture.
Hardness 2.5-4
Density 2.77-2.88
Color From colorless to white or gray, sometimes in yellow, green, brown, red or violet nuances.
Streak White.
Luster Vitreous to pearly.
Description It was mined once to be used as oven windows and insulators in electronics.
Occurance A very common mineral. Often occuring in granites and pegmatites, but also in metamorphic rocks as schist and gneiss.
Associates  
Notes The blades are flexible but breaks before they breaks.
Other varities are :
  • Sericite - fine crystallised muscovite.
  • Oncosine - crypto crystalline variety.
  • Alurgite - red manganeese magnesium containing muscovite
  • Damourite - small crystal variety with pearly lustre.
  • Mariposite - red chromian muscovite.
  • Pyrofysalite - topase almost transformed into damourite.
  • Fuchsite - Green chromium containing muscovite.
  • Oellacherite - barium muscovite, not found in Sweden.
  • Phengite - Muscovite variety.
Locations A very common mineral that's been mined in a couple of localities.
  • Väne Ryr quartz quarry, Västergötland.
  • Brattåsgruvan, Bohuslän.
  • Forshammar quartz quarry, Västmanland.
  • Västerby quartz quarry, Närke.
  • Perstorp quartz quarry, Östergötland.
  • Tangen, Jämtland.
  • Avardo, Jämtland.
  • Varuträsk pegmatite, Västerbotten.

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Last changed : 1998-08-10