Mica (Muscovite)
Muscovite (IMA approved) · Mineral Specimen / Industrial Mineral
Crystal System
Monoclinic; typically occurs in plate-like, lamellar, or foliated masses (books)
Mineral Group
Silicates; Phyllosilicate (Mica Group)
Chemical Formula
KAl2(AlSi3O10)(OH)2
Formation Process
Igneous (pegmatites), Metamorphic (schists, gneisses), or Hydrothermal (alteration zones)
About This Crystal
The specimen displays as silvery-white to brownish foliated sheets embedded in a host matrix. It expresses a distinct pearly to metallic luster on the cleavage faces, with a flaky, layered appearance and translucent transparency in thin sheets.
Physical Characteristics
Color: Colorless, silvery, or light brown; Streak: White; Cleavage: Perfect basal (one direction); Fracture: Micaceous/Uneven; Specific Gravity: 2.76-2.88; Tenacity: Elastic and flexible.
Optical Properties
Refractive Index: 1.552-1.618; Birefringence: 0.035-0.054; Biaxial negative; Weak pleochroism in colored varieties.
Hardness & Durability
Origin Region
Global distribution; notable sources include India, Brazil, Russia, and USA (North Carolina/South Dakota)
Hardness & Durability
Mohs Hardness: 2.0-2.5 on cleavage faces, up to 4 across cleavage. Toughness is low due to easy splitting between layers.
Care & Maintenance
Clean with a soft brush only; avoid water as it can seep between layers. Store in a protected container to prevent flaking. Very sensitive to physical impact.
Rarity & Value
Abundant; generally low value for common specimens. Industrial value is high as an insulator; collector value depends on 'book' size and clarity.
Special Characteristics
Exceptional basal cleavage allowing it to be split into paper-thin, flexible sheets. It is an excellent electrical and thermal insulator.
Lore & History
Historically used as 'Muscovy glass' for windows in Russia. Traditionally associated with mental clarity and self-reflection in metaphysical lore; linked to the Third Eye and Crown chakras.