metamorphic
Mica Schist
Mica Schist (primarily Muscovite and/or Biotite composition)
Hardness: 3.5-4 Mohs scale; Color: Silvery-gray, greenish-gray, or brownish; Luster: Pearly to metallic (highly reflective); Crystal Structure: Monoclinic (foliated); Cleavage: Perfect basal cleavage in individual mica flakes; Specific Gravity: 2.7-3.0
- Hardness
- 3
- Color
- Silvery-gray, greenish-gray, or brownish
- Luster
- Pearly to metallic (highly reflective)
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Physical properties
Hardness: 3.5-4 Mohs scale; Color: Silvery-gray, greenish-gray, or brownish; Luster: Pearly to metallic (highly reflective); Crystal Structure: Monoclinic (foliated); Cleavage: Perfect basal cleavage in individual mica flakes; Specific Gravity: 2.7-3.0
Formation & geological history
Formed through the regional metamorphism of shale or clay-rich sedimentary rocks under intermediate pressure and temperature conditions. It typically dates to various orogenic (mountain-building) events throughout Earth's history.
Uses & applications
Used primarily as decorative stone, in garden landscaping, flagstone for walkways, and occasionally as a source of filler in construction materials. Highly micaceous specimens are used in electrical insulation.
Geological facts
The term 'Schist' is derived from the Greek word 'schistos,' meaning 'to split,' referring to the rock's tendency to peel into thin layers. This specific specimen exhibits a high degree of 'schistosity,' the parallel alignment of mineral grains.
Field identification & locations
Identify in the field by its distinct layered appearance and 'glittery' reflection when hit by light. It is commonly found in mountain belts such as the Appalachians or Alps. Collectors should look for garnets often embedded within the layers.
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