igneous
Rounded dark volcanic pebble, likely basalt
Basalt (fine-grained mafic volcanic rock; identification is visual and provisional)
AI-generated identification · may be incorrectDark gray to black, fine-grained and rounded by abrasion, with small pale mineral grains or pits; basalt typically has Mohs hardness around 6, a dull to slightly lustrous surface, and no visible cleavage. The image does not show enough detail to confirm its exact composition.
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Physical properties
Dark gray to black, fine-grained and rounded by abrasion, with small pale mineral grains or pits; basalt typically has Mohs hardness around 6, a dull to slightly lustrous surface, and no visible cleavage. The image does not show enough detail to confirm its exact composition.
Formation & geological history
Basalt forms when iron- and magnesium-rich lava cools rapidly at or near the surface; basaltic rocks range from recent to billions of years old. This pebble’s smooth shape suggests transport and wear by water or sediment.
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, dense, fine-grained pebble with few visible crystals is consistent with basalt; inspect a fresh break for a uniformly fine texture. Similar-looking rocks can include other volcanic stones, so a close-up or testing would be needed for certainty.
