muscovite
muscovite crystals from North Carolina, United States
muscovite crystals with beryl crystals of Shigar in Pakistan
Detailed sheet
muscovite
Discovered by the famous mineralogist James Dwight Dana in 1850, it owes its name to the “glass of Moscow” (vitrum muscoviticum), as the large plates, heat-resistant were used as windows for stoves and furnaces in this region.
The hardness varies from one to two depending on whether it is measured in the direction of the lamellae or perpendicular.
Green fuchsite is a green variety rich in chromium.
CHEMICAL CHARACTERISTICS
KAl2[AlSi3O10](OH,F)2
aluminium and potassium silicate mineral
PHYSICAL CHARACTERISTICS
Main color
colourless
Other colors
brown, grey, yellow, pink, green, purple
Color of streak
white
Luster
pearly, vitreous
Hardness
2.0 to 4.0
Density
2.77 to 2.88
Cleavage
perfect
Fracture
uneven
disintegrates into transparent and flexible strips
OPTICAL PROPERTIES
Transparency
translucent, transparent
Refractive index
1.552 - 1.620
Double refraction
0.035
definite, biaxial
visible double refraction
No
Dispersion
-
Pleochroism
variable
Number of colors
2
can only be seen in very colored stones : colorless, yellow green
Fluorescence
none
CRYSTALS PROPERTIES
characteristic crystals pseudo-hexagonal, lamellar
crystals system
monoclinic
OTHER INFORMATIONS
APPROACHING GEMS
Exploited
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This is a very common mineral, one of the components of the granite (white mica, flake, thin strips). It is found in the whole world. Very large crystals whose cleavage can provide leaves of several tens of cm. come from Madagascar and Brazil.
use in jewelry
Before the eighteenth century, it was used to replace windows, as they were very expensive, brittle and sensitive to heat. It was used for the windows of houses in Russia, for those of vessels (elasticity enabled it to withstand the detonations of gunfire) and lanterns. Very rarely used in jewelry.
Other
Gems
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