metamorphic

Biotite-rich schist (mica schist)

Mica schist, chiefly quartz + biotite mica; approximate formula for biotite K(Mg,Fe)₃AlSi₃O₁₀(F,OH)₂

AI-generated identification · may be incorrect

Typically Mohs 2.5–3 for biotite and ~7 for quartz; gray-brown, sparkly, foliated, with a silky to vitreous luster. Visible mica flakes and aligned layers create schistosity; cleavage is strong in mica.

Identified September 4, 2026More metamorphic →

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At a glance

Common name: Biotite-rich schist (mica schist)
Scientific name: Mica schist, chiefly quartz + biotite mica; approximate formula for biotite K(Mg,Fe)₃AlSi₃O₁₀(F,OH)₂
Category: metamorphic
Identified: September 4, 2026
Method: Standard

AI Estimated Value

About $5–$25 for a common hand specimen; $25–$75 for unusually large, fresh, or aesthetically striking pieces.

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 regional metamorphism, commonly during mountain building; age depends on locality and may range from Precambrian to Phanerozoic.

Uses & applications

Used locally as decorative stone, landscaping rock, and occasionally building material, though foliation limits durability. Attractive specimens are collected for their reflective mica texture.

Geological facts

The specimen’s glittering flakes and planar fabric strongly suggest mica schist rather than granite; darker flakes are likely biotite, with minor quartz and feldspar.

Field identification & locations

Identify it by abundant visible mica, pronounced foliation, and layers that may split along aligned minerals; common in metamorphic mountain belts worldwide, including the Appalachians, Rockies, Alps, and Scandinavia.