metamorphic
Mica schist
Muscovite–biotite schist, composed mainly of mica and quartz
AI-generated identification · may be incorrectTypically silver, gray, brown, or bronze with a strongly foliated, flaky texture and pearly to vitreous luster. Mica has Mohs hardness 2–3 and perfect basal cleavage; quartz is hardness 7. The specimen appears weathered and iron-stained.
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Physical properties
Typically silver, gray, brown, or bronze with a strongly foliated, flaky texture and pearly to vitreous luster. Mica has Mohs hardness 2–3 and perfect basal cleavage; quartz is hardness 7. The specimen appears weathered and iron-stained.
Formation & geological history
Formed when shale or another clay-rich sedimentary rock underwent regional metamorphism, commonly during mountain building. Its exact geological age cannot be determined from the photograph; schists range from Precambrian to recent tectonic belts.
Uses & applications
Used locally as decorative stone, landscaping material, and occasionally aggregate; attractive pieces may be collected, but mica-rich schist is generally unsuitable for high-wear construction surfaces because it splits along foliation.
Geological facts
The glittering flakes are likely muscovite and/or biotite mica, while lighter granular areas may contain quartz and feldspar. The rusty zones reflect oxidation of iron-bearing minerals.
Field identification & locations
Identify it by visible aligned mica flakes, pronounced layering, and easy splitting into thin sheets; common in regional metamorphic terrains worldwide. A hand lens and streak, cleavage, and hardness tests help distinguish it from phyllite.
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