metamorphic
Likely biotite-rich schist
Mica schist, probably containing biotite and quartz (exact identification requires testing)
AI-generated identification · may be incorrectDark, shiny flaky grains mixed with pale granular material suggest biotite mica and quartz. Biotite is Mohs 2.5–3 with perfect basal cleavage; quartz is Mohs 7, vitreous, and lacks cleavage.
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Physical properties
Dark, shiny flaky grains mixed with pale granular material suggest biotite mica and quartz. Biotite is Mohs 2.5–3 with perfect basal cleavage; quartz is Mohs 7, vitreous, and lacks cleavage.
Formation & geological history
Schist forms when pre-existing clay-rich or sedimentary rocks are recrystallized under heat and pressure; its age depends on the locality and cannot be determined from the image.
Uses & applications
Schist is mainly a teaching and collecting specimen; some varieties are used as decorative stone or aggregate, but mica-rich pieces are generally unsuitable for durable construction.
Geological facts
The sparkly brown-black sheen is consistent with mica, whose thin sheets split readily along flat planes.
Field identification & locations
Look for visible, aligned or flaky mica grains and pale quartz; this small, weathered specimen is not diagnostic, and similar appearances occur in other metamorphic rocks. Mica schists occur in metamorphic belts worldwide.
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