metamorphic

Biotite-rich schist (probable mica schist)

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

AI-generated identification · may be incorrect

Dark brown-gray, sparkly micaceous surface with visible flaky crystals and weak foliation; quartz gives scattered white grains. Hardness is about 2.5–3 for biotite and 6–7 for quartz, with glassy to pearly luster and excellent mica cleavage.

Identified September 15, 2026More metamorphic →

Explore Biotite-rich schist (probable mica schist) in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

At a glance

Common name: Biotite-rich schist (probable mica schist)
Scientific name: Mica schist; chiefly quartz (SiO₂), biotite [K(Mg,Fe)₃AlSi₃O₁₀(F,OH)₂], and feldspar
Category: metamorphic
Identified: September 15, 2026
Method: Standard

AI Estimated Value

About $5–$25 for a common hand specimen; $30–$100+ for large, fresh, strongly foliated or aesthetically attractive 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, typically during mountain building; its exact geological age cannot be determined from the image. Flattened and aligned mica produces the schistose texture.

Uses & applications

Used locally as decorative stone, landscaping material, and occasionally wall or paving stone; generally unsuitable for high-strength construction because it splits along foliation. Attractive specimens are collected for their sparkle.

Geological facts

The reflective flakes are likely biotite mica, while pale grains are quartz or feldspar. A fresh surface commonly reveals stronger foliation than the weathered exterior.

Field identification & locations

Identify by rubbing or breaking a fresh edge: thin elastic-to-brittle dark mica flakes separate readily, while quartz grains resist scratching. Common in metamorphic mountain belts worldwide, including the Appalachians, New England, Scandinavia, and the Alps.