igneous
Biotite-rich granite (mica granite)
Coarse-grained granitoid, chiefly quartz, feldspar, and biotite mica
AI-generated identification · may be incorrectVisible interlocking grains include shiny dark biotite, pale quartz, and pinkish feldspar. Mohs hardness is roughly 6–7 overall; biotite has sheet cleavage, while the rock has no uniform crystal shape or cleavage.
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Physical properties
Visible interlocking grains include shiny dark biotite, pale quartz, and pinkish feldspar. Mohs hardness is roughly 6–7 overall; biotite has sheet cleavage, while the rock has no uniform crystal shape or cleavage.
Formation & geological history
Formed as silica-rich magma cooled slowly underground, allowing coarse crystals to grow. Its age cannot be determined from the image; granites occur across many geological periods.
Uses & applications
Used as dimension stone, paving and construction aggregate, and sometimes as a decorative or educational specimen.
Geological facts
The contrasting light and dark minerals are characteristic of many granites; the dark flakes appear to be mica, though a photograph cannot confirm the mineral identification.
Field identification & locations
Look for coarse, interlocking grains of quartz and feldspar with reflective, platy black mica. Granite is widespread in continental crust; a hand specimen of this size commonly sells for about $5–$20.
