metamorphic

Biotite mica schist (probable)

Mica schist, dominated by biotite; approximate mica formula K(Mg,Fe)₃AlSi₃O₁₀(OH)₂

AI-generated identification · may be incorrect

Brown-black, silvery reflective mica flakes produce a sparkly sheen and schistose foliation; mica hardness is about Mohs 2.5–3, with perfect basal cleavage, while quartz/feldspar grains are harder (6–7). The specimen appears fine- to medium-grained and foliated, though an image alone cannot confirm exact composition.

Identified September 4, 2026More metamorphic →

Explore Biotite mica schist (probable) in the encyclopedia →

Identify your own rocks.

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

App Store Google Play

Physical properties

Formation & geological history

Formed when clay-rich sedimentary rock was subjected to regional metamorphism, typically during mountain building, causing mica crystals to align; ages vary widely from Precambrian to younger orogenic belts.

Uses & applications

Used mainly as a collectible or teaching specimen; larger schist masses may serve as decorative stone, landscaping material, or low-grade building stone, but mica-rich pieces are generally unsuitable for high-wear construction.

Geological facts

Its glitter comes from reflective cleavage surfaces rather than metallic metal. The brown coloration commonly reflects iron-rich biotite and weathering.

Field identification & locations

Look for platy flakes that split into flexible sheets, strong foliation, and mica sparkle; common in metamorphic mountain belts worldwide, including the Appalachians, Alps, and Scandinavia. A hand lens and streak/cleavage tests help distinguish it from glittery ore.