igneous
Weathered granite or granitic gneiss
Granite; primarily quartz, feldspar, and mica
AI-generated identification · may be incorrectGray-brown, fine- to medium-grained, dull to slightly sparkly surface with visible quartz/feldspar specks; hardness about 6–7 Mohs, no obvious cleavage as a whole, and typical specific gravity 2.6–2.8. The rounded shape and darkened surface indicate weathering or abrasion.
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Physical properties
Gray-brown, fine- to medium-grained, dull to slightly sparkly surface with visible quartz/feldspar specks; hardness about 6–7 Mohs, no obvious cleavage as a whole, and typical specific gravity 2.6–2.8. The rounded shape and darkened surface indicate weathering or abrasion.
Formation & geological history
Likely crystallized slowly from silica-rich magma deep in the crust, generally during Precambrian to Phanerozoic continental crust formation; subsequent uplift and weathering rounded the specimen. The photograph is insufficient to distinguish granite confidently from weathered gneiss or another felsic rock.
Uses & applications
Common granite is widely used as crushed aggregate, building stone, monuments, countertops, and landscape rock; ordinary hand specimens have little commercial value.
Geological facts
Quartz appears glassy or gray, feldspar is commonly pale pink/white, and mica may produce reflective flakes. Strong banding would favor gneiss, while uniform interlocking grains favor granite.
Field identification & locations
Look for interlocking quartz and feldspar grains, occasional dark mica, and a granular texture; test hardness against glass and inspect a fresh chip with a hand lens. Common worldwide in continental mountain belts and exposed shields.
