igneous
Weathered granite or granitic gneiss pebble
Granite: quartz + feldspar + mica; possibly weakly foliated gneiss
AI-generated identification · may be incorrectCoarse, interlocking grains with pale tan/white feldspar, translucent gray quartz, and dark biotite or amphibole. Mohs hardness about 6–7; vitreous quartz, blocky feldspar, no obvious cleavage as a whole; typical specific gravity 2.6–2.8.
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Physical properties
Coarse, interlocking grains with pale tan/white feldspar, translucent gray quartz, and dark biotite or amphibole. Mohs hardness about 6–7; vitreous quartz, blocky feldspar, no obvious cleavage as a whole; typical specific gravity 2.6–2.8.
Formation & geological history
Formed by slow crystallization of silica-rich magma deep in the continental crust, generally Precambrian to Phanerozoic in age, then exposed and rounded by weathering and transport.
Uses & applications
Used as crushed aggregate, road stone, building stone, monuments, and countertops; attractive polished pieces are collected but this small weathered pebble has little commercial value.
Geological facts
Granite is not a single mineral but a rock defined by abundant quartz and feldspar. The rusty brown surface likely reflects oxidation of iron-bearing mica or amphibole.
Field identification & locations
Look for visible interlocking quartz, feldspar, and dark mica grains; granite is tougher and more crystalline than sandstone. Common in continental mountain belts, glacial deposits, stream gravels, and landscaping stone.
