igneous
Likely basalt or scoria fragment
Dark mafic volcanic rock, most likely basalt (plagioclase–pyroxene–olivine) or vesicular scoria
AI-generated identification · may be incorrectVery dark gray to black, apparently fine-grained and dull; likely hardness about 5–6, with no visible cleavage. The silhouette suggests an irregular, possibly porous volcanic fragment, but lighting and low image detail prevent reliable texture identification.
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Physical properties
Very dark gray to black, apparently fine-grained and dull; likely hardness about 5–6, with no visible cleavage. The silhouette suggests an irregular, possibly porous volcanic fragment, but lighting and low image detail prevent reliable texture identification.
Formation & geological history
Forms when iron- and magnesium-rich lava cools rapidly at or near Earth’s surface; basalt commonly ranges from Cenozoic to Precambrian age, while scoria forms during relatively recent eruptions. Common sources include volcanic fields, lava flows, and cinder cones.
Uses & applications
Basalt is used as crushed aggregate, road stone, riprap, and building stone; attractive pieces may be collected, but this specimen has little apparent gem value.
Geological facts
Basalt is the most abundant volcanic rock in Earth’s oceanic crust. Scoria is lighter and more vesicular than ordinary basalt because gas bubbles were trapped during eruption.
Field identification & locations
Identify it by black color, fine grain, high density, and possible gas cavities; a streak test, close inspection, and density test would distinguish basalt from scoria or slag. Common locations include Hawaii, Iceland, the Pacific Northwest, India, and volcanic regions worldwide.
