igneous
Dark rounded pebble, likely basalt or slag
Probable fine-grained mafic rock; possibly basalt (plagioclase–pyroxene) or industrial iron/steel slag
AI-generated identification · may be incorrectSmall, smooth, dark gray-brown, and weakly lustrous with a fine-grained texture; hardness is approximately 5–7 Mohs if basalt, though hardness and density cannot be confirmed visually. No visible cleavage or crystals are apparent.
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Physical properties
Small, smooth, dark gray-brown, and weakly lustrous with a fine-grained texture; hardness is approximately 5–7 Mohs if basalt, though hardness and density cannot be confirmed visually. No visible cleavage or crystals are apparent.
Formation & geological history
If natural basalt, it formed from rapidly cooled mafic lava, commonly in the Cenozoic or younger volcanic settings. Its unusually uniform rounded shape could also indicate beach/stream abrasion or human-made slag.
Uses & applications
Basalt is used as aggregate, road material, and dimension stone; slag has industrial value as aggregate but little collector value. This specimen is generally not suitable for jewelry.
Geological facts
The image also shows many loose dark grains, which may be sand or debris rather than material shed from the pebble. A magnet, streak, and fresh fracture would help distinguish basalt from iron-rich slag.
Field identification & locations
Common possibilities include basaltic volcanic regions, riverbeds, beaches, landscaping gravel, or industrial areas. Basalt typically has a dull, compact surface; slag may show glassy patches, bubbles, metallic specks, or strong magnetism.
