mineral
Muscovite Mica
KAl2(AlSi3O10)(F,OH)2
AI-generated identification · may be incorrectHardness: 2-2.5 on Mohs scale; Color: Colorless, silvery, or light brown; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect basal cleavage (easily splits into thin, flexible sheets); Specific gravity: 2.76-3.00
- Hardness
- 2-2
- Color
- Colorless, silvery, or light brown
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 2-2.5 on Mohs scale; Color: Colorless, silvery, or light brown; Luster: Vitreous to pearly; Crystal structure: Monoclinic; Cleavage: Perfect basal cleavage (easily splits into thin, flexible sheets); Specific gravity: 2.76-3.00
Formation & geological history
Forms in igneous rocks like pegmatites and granites, as well as metamorphic rocks such as schists and gneisses. It forms from the cooling of silica-rich magma or through the metamorphism of clay-rich rocks.
Uses & applications
Used as an electrical insulator in electronics, as a lubricant, in the manufacture of drywall joint compounds, in cosmetics (lipstick and nail polish) for shimmer, and in specialty windows for high-temperature ovens.
Geological facts
Muscovite was historically used as a cheaper alternative to glass for windows in Russia, leading to its nickname 'Muscovy-glass'. The sheets are heat-resistant and perfectly transparent when thin.
Field identification & locations
Identify in the field by its 'books' of sheets that can be peeled apart with a fingernail and its reflective, shimmery surface. Commonly found in Brazil, India, and the United States (North Carolina).
