igneous
Rounded granite cobble
Granite; chiefly quartz, feldspar, and mica/amphibole
AI-generated identification · may be incorrectCoarse-grained, speckled gray-beige rock with black minerals; interlocking crystals, vitreous to dull luster, no cleavage as a whole, and Mohs hardness about 6–7. Its rounded shape indicates water or glacial abrasion.
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Physical properties
Coarse-grained, speckled gray-beige rock with black minerals; interlocking crystals, vitreous to dull luster, no cleavage as a whole, and Mohs hardness about 6–7. Its rounded shape indicates water or glacial abrasion.
Formation & geological history
Granite crystallizes slowly from silica-rich magma deep in the continental crust, commonly during Precambrian to Phanerozoic plutonic events. This specimen was later exposed and rounded by weathering, rivers, beaches, or glaciers.
Uses & applications
Used extensively as dimension stone, countertops, paving, monuments, aggregate, and landscaping rock; attractive polished pieces may be decorative but are generally low-value.
Geological facts
The visible grains likely include translucent quartz, pale potassium/plagioclase feldspar, and dark biotite or hornblende. Exact identification is limited by the photograph; it could be a closely related granodiorite.
Field identification & locations
Identify by its coarse interlocking grains, abundant light feldspar/quartz, and scattered dark mica or amphibole; it should not fizz with dilute acid. Common worldwide in continental mountain belts and glacial or river deposits.
