metamorphic

Biotite-rich schist (probable mica schist)

Mica schist; predominantly quartz, biotite, and feldspar

AI-generated identification · may be incorrect

Typically Mohs 2.5–7 depending on mineral and orientation; dark brown-gray, foliated, and micaceous with a sparkly or satiny luster. Strong schistosity allows splitting along aligned mica layers; density is usually about 2.6–2.9 g/cm³.

Identified September 3, 2026More metamorphic →

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Physical properties

Formation & geological history

Formed when shale or another clay-rich sediment was subjected to regional metamorphism, commonly during mountain building. Its exact geological age cannot be determined from the photograph; ages vary widely by terrain.

Uses & applications

Used locally as dimension stone, landscaping material, and aggregate, though pronounced foliation limits structural applications. Attractive pieces may be collected or used decoratively.

Geological facts

The visible layered, glittering texture reflects aligned mica flakes produced by directed pressure and heat. It may grade into phyllite at lower metamorphic grade or gneiss at higher grade.

Field identification & locations

Identify it by visible foliation, glittering mica, irregular splitting, and a coarse metamorphic texture; a hand lens should reveal platy biotite or muscovite. Common in regional metamorphic belts worldwide, including the Appalachians, Alps, and Precambrian terrains.