A
thin cleavage fragment of Muscovite with aligned inclusions of Hematite, from
Brazil.
A
cleaved crystal of Muscovite with inclusion of Beryl from South Dakota.
Diamond shaped Muscovite crystals
Fuschite is the green chromian
variety of Muscovite.
CHEMISTRY KAl2(Si3Al)O10(OH,F)2
CRYSTALLOGRAPHY Monoclinic
CRYSTAL GROWTH AND HABITS Muscovite is tabular to columnar. It is commonly pseudohexagonal or diamond shaped. It also forms masses that are plumose, scaly, globular or massive.
COLOR AND OTHER OPTICAL PROPERTIES Colorless, gray, brownish, green, yellow and rose; transparent to translucent
HARDNESS 2.5 across cleavage sheets and 4 along the sides of the crystals (perpendicular to cleavage direction)
SPECIFIC GRAVITY 2.7 - 2.8
LUSTER Vitreous to pearly
STREAK White
BREAKABILITY Perfect cleavage in 1 direction producing very thin elastic sheets, uneven fracture
OCCURRENCE A common rock forming mineral in granite, gneiss, schist and granite pegmatites.
ASSOCIATED MINERALS Quartz, Plagioclase feldspars, Potassium fledspars, Biotite, Tourmaline, Beryl, Garnet