metamorphic

Likely raw mica-bearing metamorphic rock or mineral fragment

Tentatively biotite schist; visually similar dark mica-rich material

AI-generated identification · may be incorrect

Dark gray-green, flaky/foliated texture with a dull to vitreous luster; likely Mohs 2.5–3 if biotite-rich, with excellent basal cleavage. Individual crystals may show platy layers, but the small, blurred specimen prevents confident identification.

Identified September 8, 2026More metamorphic →

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Physical properties

Formation & geological history

Biotite schist forms when clay-rich sedimentary or igneous protoliths undergo regional metamorphism, commonly during mountain building; ages vary from Precambrian to recent tectonic belts. It may also be a loose mica crystal or altered mafic fragment.

Uses & applications

Usually used as a teaching or collecting specimen; mica-rich schist can be used decoratively or as aggregate, while biotite has limited industrial value. Not typically a gemstone.

Geological facts

Biotite splits into thin, flexible sheets and commonly occurs with quartz, feldspar, and garnet. A dark green-black color can also indicate chlorite, amphibole, or serpentine, so a definitive ID requires testing.

Field identification & locations

Look for elastic flakes, perfect one-direction cleavage, and a white-to-gray streak; a hardness test and loupe examination would help distinguish mica from amphibole or chlorite. Common in metamorphic terrains worldwide.