igneous
Unidentified dark rock fragment
Likely basalt or fine-grained mafic rock; exact identification is uncertain from the photograph
AI-generated identification · may be incorrectDark gray-black, dull to faintly waxy luster, irregular angular fracture, and apparently fine-grained texture. Typical basalt hardness is about Mohs 6, with no visible cleavage and specific gravity around 2.8–3.0.
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Physical properties
Dark gray-black, dull to faintly waxy luster, irregular angular fracture, and apparently fine-grained texture. Typical basalt hardness is about Mohs 6, with no visible cleavage and specific gravity around 2.8–3.0.
Formation & geological history
Basalt forms when iron- and magnesium-rich lava rapidly cools at or near Earth’s surface, commonly in volcanic flows; specimens may range from recent to Precambrian in age.
Uses & applications
Used as crushed aggregate, road base, riprap, and construction stone; ordinary fragments have negligible jewelry or collector value.
Geological facts
The image lacks scale, visible crystals, and diagnostic features, so it could also be another dark volcanic rock or slag-like material.
Field identification & locations
Look for a dense, nonmagnetic-to-weakly magnetic, fine-grained stone with tiny feldspar or pyroxene crystals; a streak test, magnet test, fresh fracture, and hand lens would improve identification. Basalt is widespread in volcanic regions and oceanic crust.
