metamorphic
Mica-rich schist
Muscovite–biotite quartz schist, composition variable
AI-generated identification · may be incorrectTypically gray to silvery, with glittering platy mica and uneven foliation; quartz gives a glassy luster. Hardness is about 2–3 for mica and 7 for quartz; specific gravity commonly 2.6–2.8, with no consistent cleavage for the whole rock but excellent mica cleavage.
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Physical properties
Typically gray to silvery, with glittering platy mica and uneven foliation; quartz gives a glassy luster. Hardness is about 2–3 for mica and 7 for quartz; specific gravity commonly 2.6–2.8, with no consistent cleavage for the whole rock but excellent mica cleavage.
Formation & geological history
Formed when shale or other clay-rich sediment was subjected to moderate heat and pressure during regional metamorphism, commonly during mountain building. Its exact geological age cannot be determined from the photograph.
Uses & applications
Used locally as decorative stone, landscaping material, and occasionally wall or roofing stone; most specimens have modest collector value.
Geological facts
The visible sparkle comes from mica flakes reflecting light, while the layered texture records directed metamorphic pressure. Schist commonly represents a metamorphic grade higher than slate or phyllite.
Field identification & locations
Identify it by its strongly foliated, flaky texture and mica sparkle; it may split along wavy layers and is softer than granite. Common in metamorphic mountain belts worldwide, including the Appalachians, Alps, and Himalayas.
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