igneous
Likely gray granitic rock
Granite or granodiorite; chiefly quartz, feldspar, and mica/amphibole
AI-generated identification · may be incorrectCoarse-grained, gray, speckled, and moderately crystalline with a dull to vitreous luster; typical hardness is about 6–7 Mohs, with no consistent cleavage as a whole. The photograph is slightly blurred, so exact identification is uncertain.
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Physical properties
Coarse-grained, gray, speckled, and moderately crystalline with a dull to vitreous luster; typical hardness is about 6–7 Mohs, with no consistent cleavage as a whole. The photograph is slightly blurred, so exact identification is uncertain.
Formation & geological history
Forms when silica-rich magma cools slowly deep underground, producing interlocking crystals; most specimens formed during Precambrian to Phanerozoic continental-crust events. Common in exposed plutons and glacial gravel deposits.
Uses & applications
Widely used as building stone, countertops, paving, monuments, aggregate, and decorative rock; ordinary hand specimens have little commercial value.
Geological facts
The dark grains may be biotite mica or amphibole, while pale grains are feldspar and quartz. Granodiorite differs from granite by having more plagioclase feldspar.
Field identification & locations
Look for visible interlocking light and dark grains, a hard surface that can scratch glass, and generally pale gray coloration; acid testing is usually not diagnostic. Common worldwide, especially in mountain belts and glacial deposits.
