metamorphic

Biotite-rich schist (likely mica schist)

Mica schist; chiefly quartz (SiO₂), biotite [K(Mg,Fe)₃AlSi₃O₁₀(F,OH)₂], feldspar, and minor sulfides/iron oxides

AI-generated identification · may be incorrect

Typically gray to dark brown, with sparkly platy mica, strong foliation, and wavy layered texture; quartz and feldspar form granular bands. Hardness is about 2.5–3 for biotite and 6–7 for quartz; nonmetallic to pearly luster, with mica cleavage and no consistent crystal shape in the whole rock.

Identified September 2, 2026More metamorphic →

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At a glance

Common name: Biotite-rich schist (likely mica schist)
Scientific name: Mica schist; chiefly quartz (SiO₂), biotite [K(Mg,Fe)₃AlSi₃O₁₀(F,OH)₂], feldspar, and minor sulfides/iron oxides
Category: metamorphic
Identified: September 2, 2026
Method: Standard

AI Estimated Value

Common hand specimens: $5–$20; unusually colorful, garnet-bearing, or well-displayed specimens: $25–$100.

Not an official valuation

AI estimate for general interest only — not an appraisal. Actual value depends on condition, provenance, and market demand. Verify with a professional before buying, selling, or insuring.

This identification was generated by AI and may contain errors. Verify important details before relying on them — and never use an AI result to judge whether a specimen is safe to handle. Read the full disclaimer

Physical properties

Formation & geological history

Formed when shale or other clay-rich sedimentary rock underwent regional metamorphism under directed pressure and elevated temperature, commonly during mountain building. Its exact age cannot be determined from the image and may range from Paleozoic to Precambrian depending on locality.

Uses & applications

Used locally as decorative stone, landscaping material, and occasionally building facing; abundant mica schist has limited commercial value because it splits and weathers readily. Attractive specimens are collected for their foliation and reflective mica.

Geological facts

The glitter comes mainly from aligned biotite or muscovite sheets, while yellow-brown patches may be iron oxidation or sulfide weathering. Foliation develops as mica grains recrystallize perpendicular to maximum pressure.

Field identification & locations

Identify it by its strongly layered, easily splitting structure and visible mica flakes; a glassy streak or quartz-rich bands support the identification. Common in regional metamorphic belts worldwide, including New England, the Appalachians, Scandinavia, and the Himalaya.