igneous
Dark river-worn pebble, likely basalt
Fine-grained basalt (tentative visual identification)
AI-generated identification · may be incorrectDark gray-green, rounded and smooth, with a dull to slightly waxy surface and no visible large crystals. Basalt is typically composed of plagioclase, pyroxene, and possibly olivine; Mohs hardness about 6, with no distinct cleavage. Exact composition cannot be confirmed from the image.
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Physical properties
Dark gray-green, rounded and smooth, with a dull to slightly waxy surface and no visible large crystals. Basalt is typically composed of plagioclase, pyroxene, and possibly olivine; Mohs hardness about 6, with no distinct cleavage. Exact composition cannot be confirmed from the image.
Formation & geological history
Basalt forms when mafic lava cools rapidly at or near Earth’s surface; its age depends on source. The pebble’s rounded shape likely results from prolonged transport and abrasion in water.
Uses & applications
Basalt is widely used as crushed aggregate, paving stone, and construction material; this small pebble is mainly suitable for collecting or decoration.
Geological facts
Basalt is among Earth’s most abundant volcanic rocks and also forms much of the ocean floor.
Field identification & locations
A dark, fine-grained appearance and lack of visible crystals are consistent with basalt, but other dark rocks can look similar. Common in river gravels and volcanic regions; identification would be improved by examining a fresh, unweathered surface.
