igneous
Biotite-bearing granite (likely granodiorite)
Coarse-grained granitoid, composed mainly of quartz and feldspar with dark biotite or hornblende
AI-generated identification · may be incorrectHardness about 6–7 Mohs; gray-white with black mineral patches and a granular, nonmetallic luster. Interlocking crystals; no prominent cleavage as a whole rock. Exact mineral proportions cannot be confirmed from the image.
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Physical properties
Hardness about 6–7 Mohs; gray-white with black mineral patches and a granular, nonmetallic luster. Interlocking crystals; no prominent cleavage as a whole rock. Exact mineral proportions cannot be confirmed from the image.
Formation & geological history
An intrusive igneous rock formed as silica-rich magma cooled slowly underground, allowing visible crystals to grow. Granitoids occur in ancient continental crust across many geological ages.
Uses & applications
Granite and granodiorite are used for building and paving stone, countertops, monuments, and crushed aggregate; this rounded specimen is mainly suitable for collecting or decoration.
Geological facts
The black patches are likely concentrated dark minerals such as biotite or hornblende, while the light matrix is feldspar and quartz.
Field identification & locations
Look for interlocking light quartz/feldspar grains and scattered dark minerals; the rounded shape suggests river or beach abrasion. Common worldwide in continental mountain belts and glacial deposits.
