metamorphic

Weathered mica-rich schist

Muscovite–biotite schist, possibly quartz-bearing

AI-generated identification · may be incorrect

Typically medium-grade metamorphic rock with abundant flaky mica, giving a silvery to dark gray color and sparkly micaceous luster. Micas have Mohs hardness 2–3; the rock commonly has pronounced foliation and splits along mica-rich planes, while quartz and feldspar are harder (about 6–7).

Identified September 19, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when shale or other clay-rich sediment was buried, heated, and compressed during mountain building, recrystallizing into aligned mica and quartz; commonly Paleozoic or older, though age cannot be determined from the photograph.

Uses & applications

Used locally as decorative stone, wall stone, landscaping material, and occasionally roofing or paving slabs; strongly foliated material is generally unsuitable for structural aggregate. Attractive specimens may be collected for mineral displays.

Geological facts

The platy, glittering flakes and wavy foliation are characteristic of schistosity. Dark flakes are likely biotite, whereas pale silvery flakes are likely muscovite; weathering can produce rusty iron staining.

Field identification & locations

Look for planar layers, abundant visible mica, and easy splitting; unlike gneiss, schist usually lacks strong alternating light–dark compositional bands. Common in regional metamorphic belts worldwide, including the Appalachians, Alps, Himalaya, and Precambrian shields.