Muscovite

Big Photo

Brazil
1.94 carats
© Mineral Classics

The name Muscovite derives from its use in windows as muscovy glass, Muscovy being an old Russian Province.

Muscovite is the most common member of the Mica Group. It typically occurs as massively crystalline material in "books" or in flaky grains.

Muscovite can be pink, colourless, silver-white, yellowish, greenish with a pearly luster on cleavage faces. It often has a sparkly look.

Because of its silvery sheen, Muscovite is sometimes called cat's silver.

Muscovite Gemstones by Colour

This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
 
General Information
Varieties/Types:
Fuchsite - A greenish chromium-bearing variety of Muscovite.
Verdite - A green ornamental stone, primarily an impure Fuchsite from South Africa.
Chemical Formula
KAl
 
2
AlSi
 
3
O
 
10
(OH)
 
2
Walter Schumann, Gemstones of the world (2001)
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Photos of natural/un-cut material from mindat.org
Physical Properties of Muscovite
Mohs Hardness2 to 3
Walter Schumann, Gemstones of the world (2001)
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Specific Gravity2.78 to 2.88
Walter Schumann, Gemstones of the world (2001)
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TenacityFlexible,Elastic
Anthony et al, Handbook of Mineralogy (2001) Laminae flexible and elastic; tough.
Cleavage QualityPerfect
Walter Schumann, Gemstones of the world (2001)
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Optical Properties of Muscovite
Refractive Index1.552 to 1.618
Anthony et al, Handbook of Mineralogy (2001)
Optical CharacterBiaxial/-
Anthony et al, Handbook of Mineralogy (2001)
PleochroismWeak when colored.
Anthony et al, Handbook of Mineralogy (2001)
DispersionWeak
Anthony et al, Handbook of Mineralogy (2001)
Colour
Colour (General)Pink, colourless, silver-white, yellowish, greenish.
Walter Schumann, Gemstones of the world (2001)
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TransparencyTransparent,Translucent
Walter Schumann, Gemstones of the world (2001)
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LustreVitreous,Pearly
Walter Schumann, Gemstones of the world (2001) On cleavage surfaces mother-of-pearl lustre.More from other references
Crystallography of Muscovite
Crystal SystemMonoclinic
Walter Schumann, Gemstones of the world (2001)
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HabitCrystals tabular to columnar, striated, pseudohexagonal or diamond-shaped. As stellate aggregates, plumose, globular; scaly, granular, compact massive.
Anthony et al, Handbook of Mineralogy (2001)
Geological Environment
Where found:A common rock-forming mineral, in phyllites, schists, and gneisses; in granites, granite pegmatites, and aplites. Formed from other minerals under hydrothermal conditions; may be detrital or authigenic.
Anthony et al, Handbook of Mineralogy (2001)
Further Information
Mineral information:Muscovite information at mindat.org
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