igneous
Weathered granite or granitic gneiss cobble
Granite; chiefly quartz, feldspar, and mica
AI-generated identification · may be incorrectCoarse, mottled gray-brown to reddish surface with visible quartz/feldspar grains and dark mica; Mohs hardness about 6–7, vitreous to dull luster, no prominent cleavage as a whole, and specific gravity around 2.6–2.8.
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Physical properties
Coarse, mottled gray-brown to reddish surface with visible quartz/feldspar grains and dark mica; Mohs hardness about 6–7, vitreous to dull luster, no prominent cleavage as a whole, and specific gravity around 2.6–2.8.
Formation & geological history
Formed by slow crystallization of silica-rich magma deep in the continental crust, commonly during Precambrian to Phanerozoic mountain-building; weathering and transport rounded this specimen.
Uses & applications
Used extensively as building stone, aggregate, monuments, countertops, and landscaping rock; ordinary cobbles have little jewelry or collector value.
Geological facts
The reddish-brown coloration likely reflects iron oxidation during weathering. The image does not resolve the texture well enough to distinguish granite confidently from granitic gneiss or another feldspar-rich rock.
Field identification & locations
Look for interlocking quartz, white/pink feldspar, and black mica; gneiss usually shows foliation or banding. Common worldwide, especially in continental shields and mountain belts.
