igneous
Polished brown pebble
Likely altered basalt or mafic volcanic rock; exact identification is uncertain from the photograph
AI-generated identification · may be incorrectDark brown to gray, opaque, rounded and polished, with subtle granular texture and possible metallic flecks; likely hardness about 5–6 Mohs and no obvious cleavage. Specific gravity is probably about 2.8–3.2, typical of mafic rocks.
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Physical properties
Dark brown to gray, opaque, rounded and polished, with subtle granular texture and possible metallic flecks; likely hardness about 5–6 Mohs and no obvious cleavage. Specific gravity is probably about 2.8–3.2, typical of mafic rocks.
Formation & geological history
Probably a naturally water-worn river or beach pebble, later tumbled or polished; if basaltic, it formed from rapidly cooled lava, commonly in the Cenozoic or older. The visible brown color may reflect iron-oxide weathering.
Uses & applications
Suitable as a decorative tumbled stone, paperweight, or craft material; it has little industrial or jewelry value unless testing reveals an attractive ore or gemstone mineral.
Geological facts
The image does not show diagnostic crystals, vesicles, foliation, or layering, so basalt cannot be confirmed confidently. A streak, magnetism test, hardness test, and close examination with magnification would improve identification.
Field identification & locations
Commonly found in volcanic terrains, stream gravels, and beaches; identify by its fine-grained dark interior, lack of strong cleavage, and possible magnetism. Avoid acid testing unless carbonate minerals are suspected.
