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

Dark gray-brown, strongly sparkly platy mica, with a foliated texture and irregular fracture. Individual minerals are commonly Mohs 2.5–3.5 for biotite and about 7 for quartz; luster is vitreous to pearly. The specimen appears weathered and possibly contains minor garnet or feldspar.

Identified September 6, 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 6, 2026
Method: Standard

AI Estimated Value

About $2–$15 for a common hand specimen; up to $20–$50 if unusually attractive, labeled, or containing prominent garnet 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 other clay-rich sediment was subjected to regional metamorphism, producing aligned mica layers. Commonly Paleozoic or older, though the exact age cannot be determined from the photograph.

Uses & applications

Used locally as decorative stone, landscaping material, and occasionally building stone; attractive specimens are collected, but it is generally not a gemstone.

Geological facts

The glitter comes mainly from reflective cleavage surfaces of mica, not metallic ore. Its foliation records directed pressure during mountain building.

Field identification & locations

Look for thin, parallel mica flakes that reflect light and allow splitting along foliation, unlike massive granite. The Montréal region near 45.5°N, 73.6°W contains glacially transported Precambrian metamorphic rocks, so a local or glacial erratic schist is plausible; exact provenance is uncertain.