Description: Muscovite is the most common of the Mica group minerals. Muscovite is present in many different rock types as a primary mineral, in particular metamorphic rocks (schists).
Chemical Formula: KAl2(AlSi3O10)(OH)2
Crystal Form: Prismatic, usually in massive or platy sheets
Crystal System: Monoclinic
Color: White to colorless, silvery-white, and tinged various colors by impurities. Transparent, Translucent
Streak: White
Luster: Vitreous, Silky, Pearly
Fracture: Micaceous
Cleavage: Perfect in one direction, can be cleaved into very thin “sheets”.
Hardness: 2 ½ on Moh’s scale.
Density/Specific Gravity: 2.77 - 2.88 g/cm3
Magnetism: N/A
Taste: N/A
Hydrochloric acid: N/A
Radioactivity: N/A
Fluorescence: N/A
Distinguishing Physical Properties:
Hardness: softer than a fingernail
Cleavage: very strong in 1 direction (it can be sliced into thin sheets)
Color: light colored or colorless
Photograph Attribution: Muscovite specimen photograph by Sean C. Murphy, 2020.