igneous
Weathered granite or granitic gneiss
Quartz–feldspar–mica aggregate; possibly deformed granitic gneiss
AI-generated identification · may be incorrectCoarse, mottled tan-brown and gray texture with visible quartz/feldspar grains and dark mica; typical hardness ~6–7 Mohs, vitreous to dull luster, no obvious cleavage as a whole, and specific gravity ~2.6–2.8.
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Physical properties
Coarse, mottled tan-brown and gray texture with visible quartz/feldspar grains and dark mica; typical hardness ~6–7 Mohs, vitreous to dull luster, no obvious cleavage as a whole, and specific gravity ~2.6–2.8.
Formation & geological history
Likely crystallized slowly from silica-rich magma deep in the crust, then exposed and rounded by weathering and abrasion; if gneissic, it underwent later high-grade metamorphism. Exact age cannot be determined from the photograph.
Uses & applications
Used as crushed aggregate, building stone, landscaping rock, and decorative material; this small weathered specimen has modest collecting value.
Geological facts
The irregular folded-looking surface may reflect mineral veining, weathering, or gneissic deformation rather than fossils. Quartz should resist scratching, while feldspar commonly shows blocky cleavage.
Field identification & locations
Common in continental crust and found worldwide, especially in old mountain belts and glacial deposits. Confirm with a hand lens, streak test, and hardness test; acid fizz would indicate carbonate instead, which is not apparent here.
