metamorphic

Foliated metamorphic rock, likely mica schist

Mica schist, chiefly quartz + biotite/muscovite; possibly chlorite-bearing

AI-generated identification · may be incorrect

Dark gray, coarse-grained, sparkly micaceous luster with weak foliation; quartz grains appear glassy. Typical hardness is about 2–7 depending on mineral, with mica cleavage and specific gravity around 2.7–3.0.

Identified September 3, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when shale or other clay-rich sediment was subjected to regional metamorphism, recrystallizing under elevated temperature and pressure. Such rocks commonly formed during Precambrian or Paleozoic mountain-building events, though age cannot be determined visually.

Uses & applications

Used locally as decorative stone, landscaping rock, wall stone, and occasionally aggregate; attractive pieces may be polished for display, but it is not usually a jewelry gemstone.

Geological facts

The glitter comes mainly from aligned mica flakes, whose planar surfaces can produce a schistose texture. The rounded shape and smooth surface indicate stream wear, glacial transport, or human tumbling rather than its original outcrop form.

Field identification & locations

Identify it by visible mica sparkle, planar fabric, and uneven breakage along foliation; a hand lens and streak/cleavage tests help distinguish it from granite or gneiss. Common in metamorphic mountain belts worldwide, including the Appalachians, Alps, and Himalaya.