metamorphic
Mica Specimen (Schist / Muscovite)
Muscovite / Biotite Mica (KAl2(AlSi3O10)(F,OH)2)
Hardness: 2.0-2.5 on Mohs scale. Color: Silver-grey, pearly brown to black. Luster: Vitreous to pearly. Crystal Structure: Monoclinic, highly perfect basal cleavage forming thin flexible sheets.
- Hardness
- 2
- Color
- Silver-grey, pearly brown to black
- Luster
- Vitreous to pearly
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Physical properties
Hardness: 2.0-2.5 on Mohs scale. Color: Silver-grey, pearly brown to black. Luster: Vitreous to pearly. Crystal Structure: Monoclinic, highly perfect basal cleavage forming thin flexible sheets.
Formation & geological history
Formed during regional metamorphism of argillaceous rocks (like shale or mudstone) under moderate pressure and temperature conditions, leading to the growth of platy mica minerals.
Uses & applications
Mica is widely used as an electrical insulator, in cosmetics for shimmer effects, in joint compound, and in high-temperature furnace windows.
Geological facts
Mica crystals can split into extremely thin, flexible, transparent sheets that were historically used as window glass (known as Muscovy glass) in medieval Russia.
Field identification & locations
Easily identified by its shiny, flaky, layered appearance and tendency to peel into thin pearly sheets. Commonly found in metamorphic terrains worldwide, especially in schist and pegmatite formations.
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