igneous
Weathered granite or granitic gneiss pebble
Granite; predominantly quartz, feldspar, and biotite/hornblende
AI-generated identification · may be incorrectCoarse-grained, pale tan-gray rock with dark mafic minerals and irregular light veins; quartz and feldspar have Mohs hardness 6–7, with no obvious cleavage in the whole specimen. It has a granular texture, dull to slightly glassy quartz luster, and moderate-to-high density (~2.6–2.8 g/cm³).
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Physical properties
Coarse-grained, pale tan-gray rock with dark mafic minerals and irregular light veins; quartz and feldspar have Mohs hardness 6–7, with no obvious cleavage in the whole specimen. It has a granular texture, dull to slightly glassy quartz luster, and moderate-to-high density (~2.6–2.8 g/cm³).
Formation & geological history
Likely crystallized slowly from silica-rich magma deep in the crust, generally during Precambrian to younger continental-crust events; the rounded shape reflects transport and abrasion in a river, beach, or glacial deposit. The dark streaking could indicate weak gneissic banding or weathered biotite-rich inclusions.
Uses & applications
Granite is widely used as dimension stone, countertops, monuments, aggregate, and paving; small rounded pieces are chiefly educational or decorative specimens. It is not typically jewelry grade.
Geological facts
Granite commonly contains interlocking quartz and feldspar crystals visible with a hand lens. Stronger mineral alignment, compositional banding, and foliation would support the name granitic gneiss rather than ordinary granite.
Field identification & locations
Look for visible quartz (gray translucent grains), pink/white feldspar, and black biotite; a steel file should not easily scratch fresh quartz-rich grains. Common in continental shields, mountain belts, river gravels, and glacial till.
