igneous
Vesicular basalt (likely)
Basalt; chiefly plagioclase, clinopyroxene, and olivine, with possible iron-oxide alteration
AI-generated identification · may be incorrectDark gray-black, fine-grained, dull to slightly glassy, with irregular vesicles and a rounded weathered surface; Mohs hardness about 5–6, no obvious cleavage, typical specific gravity 2.8–3.0. The image cannot confirm whether it is basalt rather than another dark volcanic rock.
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Physical properties
Dark gray-black, fine-grained, dull to slightly glassy, with irregular vesicles and a rounded weathered surface; Mohs hardness about 5–6, no obvious cleavage, typical specific gravity 2.8–3.0. The image cannot confirm whether it is basalt rather than another dark volcanic rock.
Formation & geological history
An extrusive mafic igneous rock formed when iron- and magnesium-rich lava cooled rapidly at or near Earth’s surface, commonly during the Cenozoic or younger volcanic activity. Its rounded form may result from water or weathering.
Uses & applications
Used as crushed aggregate, road base, riprap, paving stone, and dimension stone; attractive polished pieces may be sold as décor or educational specimens. This small ordinary specimen has minimal commercial value.
Geological facts
Vesicles are gas bubbles trapped during lava cooling; if the cavities are abundant, the rock may be called scoria. Basalt makes up much of oceanic crust and many volcanic islands.
Field identification & locations
Look for a heavy black fine-grained texture, tiny holes, and weak magnetism from magnetite; it generally lacks visible quartz and large crystals. Common worldwide in volcanic regions, including Hawaii, Iceland, India, and ocean floors.
