igneous
Rounded river pebble, likely granite or granitic gneiss
Felsic granitoid; mainly quartz (SiO₂), feldspar, and biotite/amphibole
AI-generated identification · may be incorrectHardness about 6–7 Mohs; gray-brown, granular texture, and dull to slightly vitreous luster. Interlocking crystals are visible, with no obvious cleavage on the weathered surface; specific gravity roughly 2.6–2.8.
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Physical properties
Hardness about 6–7 Mohs; gray-brown, granular texture, and dull to slightly vitreous luster. Interlocking crystals are visible, with no obvious cleavage on the weathered surface; specific gravity roughly 2.6–2.8.
Formation & geological history
Likely an ancient crystalline igneous rock formed by slow cooling of magma deep in the crust, commonly Precambrian to Paleozoic in age, then rounded by river or beach abrasion.
Uses & applications
Commonly used as aggregate, landscaping stone, riprap, and decorative pebble; this small weathered specimen has little jewelry or commercial value.
Geological facts
The rounded shape is transport-worn rather than its original geological form. Brown coloration likely reflects iron-oxide weathering of ferromagnesian minerals and feldspar.
Field identification & locations
Identify it by its speckled interlocking grains, hardness, and lack of layering or vesicles; a streak test is usually white or pale gray. Common in stream beds and glacial deposits worldwide.
