igneous
Fine-grained gray rock, possibly basalt
Basalt (tentative; likely plagioclase–pyroxene rock)
AI-generated identification · may be incorrectDark gray, dull to slightly granular, massive, and fine-grained with no visible crystals or cleavage; likely Mohs hardness about 6, though texture and composition cannot be confirmed from the image.
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Physical properties
Dark gray, dull to slightly granular, massive, and fine-grained with no visible crystals or cleavage; likely Mohs hardness about 6, though texture and composition cannot be confirmed from the image.
Formation & geological history
Basalt forms when low-silica lava rapidly cools at or near Earth’s surface, commonly in volcanic fields and oceanic crust. Its exact age and locality cannot be determined visually.
Uses & applications
Used as crushed aggregate, roadstone, riprap, railway ballast, and occasionally dimension stone; ordinary hand specimens generally have little commercial value.
Geological facts
The specimen’s rough, weathered surface and uniform dark-gray appearance are consistent with basalt, but it could also be fine-grained andesite, hornfels, or another mafic rock.
Field identification & locations
Look for a dense, dark rock with tiny interlocking crystals; a streak test, magnetism test, density, and thin-section or chemical analysis would improve identification. Common sources include volcanic regions, quarries, and glacial deposits.
