Muscovite
Image: James St. John (CC BY 2.0)
Mineral NameMuscovite
Chemical FormulaKAl₂(AlSi₃O₁₀)(OH)₂
Mohs Hardness2
Crystal Systemmonoclinic
Lustervitreous
Streak Colorwhite
Cleavageperfect basal (one direction)
Fractureuneven
Specific Gravity2.76
Colorscolorless, white, silver, pale brown, pale green
Transparencytransparent to translucent
Type LocalityRuggles Pegmatite Mine, New Hampshire, USA
Mineral GroupSilicates (Phyllosilicates, Mica Group)
Useselectrical insulator, filler in paints and plastics, decorative material, lubricant
Associated Mineralsbiotite, quartz, feldspar, tourmaline, garnet
Raritycommon
Description
Muscovite typically forms in thin, flexible, transparent to translucent sheets with a clearish-silvery to pale green color and a pearly luster, as seen in the image alongside darker biotite.
Geological Context
Muscovite is a common rock-forming mineral found in igneous rocks like granite and pegmatites, and in metamorphic rocks such as schists and gneisses, often forming during regional metamorphism.
