Mica, muscovite

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Crystals of muscovite with basal cleavage.

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Crystals of muscovite, colourless.

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Muscovite crystal structure (a sheet silicate), CrystalMaker.

Formula

K2Al4[Si6Al2O20](OH,F)4

Structure

Sheet silicate

Crystal System

Crystal system: monoclinic (-)

Physical Properties

Colour in hand specimen: colourless 
Cleavage: one, good 
Hardness: 2.5-3

Optical Properties

Colour in plane polarised light: colourless 
Pleochroism: none 
Relief: low 
Birefringence: 0.036-0.049; 2nd order pink to 3rd order yellow 
Extinction: straight

Mineral Specimens

M301 Mica, muscovite 
Lincoln County, North Carolina 
Well-formed tabular crystals showing the pseudohexangonal symmetry 
Colourless, mirror- like, metallic lustre 
Platy, flaky habit 
Soft

M302 Mica, muscovite    
Mysore, India 
Plates of mica artificially cut to shape 
Colourless 
One perfect cleavage

Rock Specimens

L110 Rhyolite, porphyritic (quartz porphyry) 
L201 Tuff 
L504 Garnet schist

Mineral Name

mica
muscovite
Mica, muscovite