metamorphic

Likely biotite-rich metamorphic rock (mica schist)

Mica schist, chiefly quartz + biotite mica; possible pyrite or sulfide grains

AI-generated identification · may be incorrect

Dark brown to bronze, sparkly platy mica with a foliated texture and uneven fracture; biotite has Mohs hardness 2.5–3 and perfect basal cleavage, while quartz is 7. Luster is mainly vitreous to pearly; exact composition requires testing.

Identified September 1, 2026More metamorphic →

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At a glance

Common name: Likely biotite-rich metamorphic rock (mica schist)
Scientific name: Mica schist, chiefly quartz + biotite mica; possible pyrite or sulfide grains
Category: metamorphic
Identified: September 1, 2026
Method: Standard

AI Estimated Value

About $5–$25 for an ordinary hand specimen; $25–$75 if unusually attractive, large, or containing well-formed sulfide crystals.

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 another clay-rich sediment was regionally metamorphosed under elevated heat and pressure, producing aligned mica layers; age depends on its source terrane. Common in mountain belts and Precambrian metamorphic complexes.

Uses & applications

Used locally as decorative stone, landscaping material, and occasionally dimension stone; attractive mica-rich pieces are mainly sold as teaching or collection specimens.

Geological facts

Bronze sparkle can resemble gold, but mica flakes are flexible and peel along flat cleavage surfaces; pyrite is harder, brassy, and commonly forms sharp cubic crystals.

Field identification & locations

Look for visible, aligned mica flakes and foliation; a streak, hardness, cleavage, and acid test help distinguish it from ore minerals. Common worldwide in metamorphic terrains, including the Appalachians, Canadian Shield, and Scandinavia.