metamorphic

Likely biotite-rich schist (mica schist)

Mica schist, chiefly quartz + biotite mica (K(Mg,Fe)₃AlSi₃O₁₀(F,OH)₂), possibly with muscovite and feldspar

AI-generated identification · may be incorrect

Medium- to coarse-grained, dark gray-brown, with a strongly glittery micaceous luster and wavy foliation; mica has perfect basal cleavage and Mohs hardness 2–3, while quartz is about 7. The specimen appears platy and sparkles as flakes reflect light.

Identified September 11, 2026More metamorphic →

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At a glance

Common name: Likely biotite-rich schist (mica schist)
Scientific name: Mica schist, chiefly quartz + biotite mica (K(Mg,Fe)₃AlSi₃O₁₀(F,OH)₂), possibly with muscovite and feldspar
Category: metamorphic
Identified: September 11, 2026
Method: Standard

AI Estimated Value

About $5–$25 for a common hand specimen; larger attractive or locality-labeled pieces may sell for $30–$75.

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 sediment was subjected to elevated temperature and pressure during regional metamorphism, commonly during mountain building. Its precise geological age cannot be determined from the photograph.

Uses & applications

Used locally as decorative stone, landscaping material, and occasionally dimension stone; most pieces are collected as teaching or display specimens rather than used for jewelry.

Geological facts

Schistosity develops as platy minerals recrystallize and align perpendicular to directed pressure. The bright flakes are likely biotite, though muscovite or other sulfide-bearing minerals may also be present.

Field identification & locations

Look for visible aligned mica flakes, easy splitting along foliation, and a sparkly surface; a streak, hardness test, and hand lens would help distinguish it from phyllite or mica-rich gneiss. Common in metamorphic belts worldwide, including the Appalachians, Alps, and New England.