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(MICA GROUP) K2Al4[Si6Al2O20](OH,F)4
Crystal system: Monoclinic
Refractive index: 1.552-1.616
Birefringence: 0.036-0.049
Cleavage: one perfect
Twinning:
Colour in PPL: colourless
Pleochroism: none or weak
Relief: low
Distinction: any colourless mica may be considered to be muscovite
Occurrence: wide range of regionally-metamorphosed rocks, less common that biotite in granites
Ceramic Occurrence: destroyed around 600-700o
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Muscovite - Cross polarized light - Granite petrofabric - Belize
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