metamorphic

Foliated mica-rich metamorphic rock, likely schist

Mica schist; predominantly quartz, feldspar, and biotite/muscovite mica

AI-generated identification · may be incorrect

Medium- to coarse-grained, gray-brown, sparkly, and weakly to moderately foliated; mica produces the reflective luster and splits along schistosity. Typical hardness is about 2–7 depending on mineral grains, with quartz near Mohs 7 and mica near 2–3; density is roughly 2.6–2.8.

Identified September 20, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when shale or another clay-rich sedimentary protolith was buried and subjected to elevated heat and directed pressure during regional metamorphism, commonly during mountain building. Exact age cannot be determined from the photograph.

Uses & applications

Used locally as decorative stone, landscaping material, aggregate, and occasionally dimension stone; attractive mica-rich pieces are collected but are generally low value.

Geological facts

The glitter is caused by aligned mica flakes rather than metallic ore. A hand lens should reveal platy mica and quartz grains, while foliation distinguishes schist from massive granite.

Field identification & locations

Common in metamorphic belts worldwide, including the Appalachians, New England, the Rocky Mountains, and many Precambrian terrains. Look for planar layers, mica flakes, and preferential splitting; a streak or hardness test can help separate it from gneiss or phyllite.