igneous
Dark pebble, likely fine-grained basalt
Basalt (tentative; exact identification requires testing)
AI-generated identification · may be incorrectDark gray to black, rounded and water-worn, with a fine-grained, subdued luster and small pale mineral flecks. Basalt typically has Mohs hardness 5–6, specific gravity about 2.8–3.0, and no prominent cleavage; the image does not show enough detail to confirm its texture or composition.
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Physical properties
Dark gray to black, rounded and water-worn, with a fine-grained, subdued luster and small pale mineral flecks. Basalt typically has Mohs hardness 5–6, specific gravity about 2.8–3.0, and no prominent cleavage; the image does not show enough detail to confirm its texture or composition.
Formation & geological history
If basalt, it formed when iron- and magnesium-rich lava cooled rapidly at or near Earth’s surface; such rocks occur from many geological periods. Its smooth shape likely results from transport and abrasion in water.
Uses & applications
Basalt is widely used as crushed aggregate, road stone, and building material; this small pebble is mainly suitable for collecting or decoration.
Geological facts
Basalt commonly contains plagioclase feldspar and pyroxene, sometimes with olivine. Rounded pebbles can lose diagnostic features, so appearance alone cannot establish the rock type.
Field identification & locations
Look for a dense, fine-grained dark rock with no visible large crystals; a streak, fresh fracture, and hand lens can help distinguish it from other dark stones. Basalt is common in volcanic regions and river or beach gravels worldwide.
