metamorphic
Weathered schist, possibly biotite–quartz schist
Mica schist; chiefly quartz, feldspar, biotite/muscovite, and minor dark accessory minerals
AI-generated identification · may be incorrectMedium- to coarse-grained, foliated rock with glittering mica, gray-brown color, and uneven platy fracture; quartz has Mohs hardness 7, while mica is about 2–3.5, with vitreous quartz and pearly mica luster; density typically 2.6–2.8 g/cm³.
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Physical properties
Medium- to coarse-grained, foliated rock with glittering mica, gray-brown color, and uneven platy fracture; quartz has Mohs hardness 7, while mica is about 2–3.5, with vitreous quartz and pearly mica luster; density typically 2.6–2.8 g/cm³.
Formation & geological history
Formed when shale or another clay-rich sediment was buried and subjected to moderate-to-high heat and pressure, producing aligned mica foliation; commonly Paleozoic or older, though age depends on locality.
Uses & applications
Used locally as decorative stone, wall veneer, landscaping aggregate, and occasionally roofing or paving; attractive pieces are collected, but it is rarely a jewelry gemstone.
Geological facts
The prominent layering and mica sparkle distinguish schist from massive granite; weathering preferentially loosens mica-rich layers and can create rusty iron-oxide staining.
Field identification & locations
Look for continuous foliation, visible mica flakes, and layers that split along schistosity; common in regional metamorphic belts worldwide, including the Appalachians, New England, Alps, and Himalaya. A hand lens and streak/acid tests help separate it from shale or gneiss.
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