igneous
Rounded dark pebble, likely basalt
Fine-grained mafic volcanic rock, probably basalt; exact identification is uncertain from the photo
AI-generated identification · may be incorrectDark gray, rounded and weathered, with a dull to slightly granular surface and no obvious large crystals. Basalt is typically composed mainly of plagioclase and pyroxene, sometimes olivine, and has Mohs hardness around 6; crystal structure is too fine-grained to distinguish here.
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Physical properties
Dark gray, rounded and weathered, with a dull to slightly granular surface and no obvious large crystals. Basalt is typically composed mainly of plagioclase and pyroxene, sometimes olivine, and has Mohs hardness around 6; crystal structure is too fine-grained to distinguish here.
Formation & geological history
Likely formed when basaltic lava cooled at or near Earth’s surface, then was rounded by transport in water or abrasion. Its geological age cannot be determined from appearance alone.
Uses & applications
A pebble of this size is mainly suitable for collecting or decoration; basalt is also widely used as crushed aggregate and paving stone.
Geological facts
The smooth shape reflects abrasion during transport, not necessarily a polished treatment.
Field identification & locations
Common in riverbeds, beaches, and glacial deposits. A fresh broken surface, heft, and a hand lens may help distinguish basalt from other dark rocks; the image alone is insufficient for certainty.
