metamorphic
Mica schist (likely biotite–muscovite schist)
Mica schist; chiefly quartz (SiO₂) plus muscovite and biotite mica, with possible garnet or graphite
AI-generated identification · may be incorrectSilvery-gray, strongly foliated, sparkly surface from platy mica, with uneven fractures and possible dark biotite/graphite bands. Hardness is variable, commonly 2–3 for mica and about 7 for quartz; mica has perfect basal cleavage, and specific gravity is roughly 2.7–3.0.
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Physical properties
Silvery-gray, strongly foliated, sparkly surface from platy mica, with uneven fractures and possible dark biotite/graphite bands. Hardness is variable, commonly 2–3 for mica and about 7 for quartz; mica has perfect basal cleavage, and specific gravity is roughly 2.7–3.0.
Formation & geological history
Formed when shale or other clay-rich sedimentary rock underwent regional metamorphism, causing mica recrystallization and alignment. Most examples formed during ancient mountain-building events, commonly Paleozoic or Precambrian, though age depends on locality.
Uses & applications
Used locally as decorative stone, landscaping material, and occasionally building facing; its main value is educational or as a specimen rather than jewelry-grade material.
Geological facts
The pronounced foliation is called schistosity. Individual mica flakes can flex or peel, while quartz grains remain hard and resistant.
Field identification & locations
Identify it by its layered, glittering foliation and abundant flaky mica; a steel nail may scratch mica-rich areas but not quartz grains. Common in metamorphic belts worldwide, including the Appalachians, New England, Scotland, India, and Brazil.
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