igneous
Small dark rock fragment (likely basalt or slag)
Tentatively basalt; exact identification is uncertain from the photograph
AI-generated identification · may be incorrectDark gray-green, irregular, fine-grained piece with a dull to slightly vitreous luster; likely Mohs hardness about 5–6, with no visible cleavage or distinct crystals. Its small size and blurred image prevent reliable assessment of texture, density, or magnetism.
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Physical properties
Dark gray-green, irregular, fine-grained piece with a dull to slightly vitreous luster; likely Mohs hardness about 5–6, with no visible cleavage or distinct crystals. Its small size and blurred image prevent reliable assessment of texture, density, or magnetism.
Formation & geological history
If basalt, it formed when iron- and magnesium-rich lava rapidly cooled, commonly in volcanic flows, and may range from recent to billions of years old. A metallic sheen or abundant vesicles could instead indicate industrial slag rather than natural rock.
Uses & applications
Basalt is used as crushed aggregate, road material, ballast, and occasionally building stone; a fragment this small has negligible commercial value.
Geological facts
Basalt commonly contains plagioclase, pyroxene, and sometimes olivine, producing its dark color. Slag can mimic basalt but often has bubbles, glassy surfaces, or unusually angular shapes.
Field identification & locations
Check for a fine-grained natural texture, lack of bubbles, and a weak response to a magnet; a streak test, density, and fresh broken surface would help distinguish basalt from slag. Common sources include volcanic terrains and landscaping gravel.
