igneous
Dark basalt-like rock
Fine-grained mafic volcanic rock, tentatively basalt (possibly scoria or andesite)
AI-generated identification · may be incorrectDark gray to black, dull to slightly vitreous, fine-grained and irregular; likely dominated by plagioclase and pyroxene, with possible iron oxides. Basalt hardness is about Mohs 5–6, with no visible cleavage and specific gravity roughly 2.8–3.0.
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Physical properties
Dark gray to black, dull to slightly vitreous, fine-grained and irregular; likely dominated by plagioclase and pyroxene, with possible iron oxides. Basalt hardness is about Mohs 5–6, with no visible cleavage and specific gravity roughly 2.8–3.0.
Formation & geological history
Likely formed when mafic lava cooled rapidly at or near Earth’s surface, commonly during the Cenozoic or older volcanic episodes; the exact age cannot be determined visually.
Uses & applications
Used as aggregate, road stone, building stone, and occasionally as a modest display specimen; this small piece has little commercial value unless it has unusual vesicles or provenance.
Geological facts
The image is somewhat blurred, so mineral grains and vesicles are difficult to resolve. Its dark, compact appearance is more consistent with basalt than with a crystalline gemstone.
Field identification & locations
Common worldwide in volcanic regions, including Hawaii, Iceland, the Deccan Traps, and oceanic crust. Confirm with a fresh surface, streak (usually gray), magnet response, density, and inspection for tiny gas cavities; a laboratory or hand-specimen test is needed to distinguish basalt from andesite or slag.
