igneous
Likely weathered gray stone, possibly basalt
Basalt (tentative; aphanitic mafic volcanic rock)
AI-generated identification · may be incorrectDark gray, fine-grained, dull to slightly waxy surface, with no visible large crystals or cleavage; typical basalt hardness is about 6 Mohs and specific gravity 2.8–3.0. The image is insufficient to confirm texture or mineral composition.
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Physical properties
Dark gray, fine-grained, dull to slightly waxy surface, with no visible large crystals or cleavage; typical basalt hardness is about 6 Mohs and specific gravity 2.8–3.0. The image is insufficient to confirm texture or mineral composition.
Formation & geological history
Basalt forms when iron- and magnesium-rich lava cools rapidly at or near Earth’s surface, commonly in volcanic fields and oceanic crust. Individual specimens may range from ancient Precambrian flows to recent eruptions.
Uses & applications
Used as crushed aggregate, roadstone, riprap, building stone, and occasionally as a polished decorative material; ordinary fragments have little jewelry value.
Geological facts
Basalt commonly contains microscopic plagioclase, pyroxene, and sometimes olivine, producing its dark color. Vesicles, if present, may later fill with zeolites, calcite, or quartz.
Field identification & locations
Look for a uniformly fine-grained dark matrix, high density, and possible tiny holes or weak magnetic response; a fresh edge and streak test help distinguish it from slate, concrete, or dark metamorphic rocks. Common worldwide, especially near volcanic regions and oceanic crust.
