igneous
Likely granite or granitic gneiss pebble
Granite, chiefly quartz (SiO₂), feldspar, and mica; exact identification is uncertain from the photo
AI-generated identification · may be incorrectCoarse-grained, speckled light gray and dark gray, with a granular texture and dull to slightly vitreous luster. Hardness is approximately 6–7 Mohs; quartz lacks cleavage, while feldspar shows cleavage.
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Physical properties
Coarse-grained, speckled light gray and dark gray, with a granular texture and dull to slightly vitreous luster. Hardness is approximately 6–7 Mohs; quartz lacks cleavage, while feldspar shows cleavage.
Formation & geological history
Likely crystallized slowly from silica-rich magma deep in the crust, commonly during Precambrian to Phanerozoic continental activity; stream or glacial transport may have rounded it.
Uses & applications
Common granite is used for aggregate, paving, building stone, countertops, and monuments; ordinary pebbles have little commercial or collector value.
Geological facts
The dark grains may be biotite or hornblende, while the pale grains are probably quartz and feldspar. A freshly broken surface would show crystals more clearly than this weathered pebble.
Field identification & locations
Identify it by visible interlocking crystals, lack of layering, and a quartz-rich granular appearance; common worldwide, especially in areas underlain by continental crust. A metal file should barely scratch it, while steel should not scratch quartz.
