igneous
Dark, rounded river pebble (likely basalt or andesite)
Unconfirmed fine-grained volcanic rock; basalt is a plausible identification
AI-generated identification · may be incorrectDark gray-brown, rounded, and fine-grained with a subdued surface sheen; individual crystals are not visible. Exact hardness, mineral composition, and specific gravity cannot be determined from the image.
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Physical properties
Dark gray-brown, rounded, and fine-grained with a subdued surface sheen; individual crystals are not visible. Exact hardness, mineral composition, and specific gravity cannot be determined from the image.
Formation & geological history
Possibly formed when lava cooled rapidly, then became rounded through transport in water; its age and geological setting are unknown.
Uses & applications
Similar pebbles are used for landscaping, decorative aggregates, and collections; this specimen appears to have little commercial value.
Geological facts
A pebble’s smooth, rounded shape commonly results from abrasion during transport, though tumbling can produce a similar appearance.
Field identification & locations
Basalt commonly contains tiny crystals of plagioclase and pyroxene. A fresh broken surface, magnification, and hardness or density tests would help distinguish it from other dark stones.
