igneous
Vesicular basalt (likely scoria)
Basaltic volcanic rock; chiefly plagioclase, pyroxene, and olivine
AI-generated identification · may be incorrectDark gray-black, fine-grained, dull to slightly glassy, with abundant vesicles and a small tan weathered/mineral-filled patch; hardness about 5–6, no obvious cleavage, typically dense but porous. The rounded shape suggests water-worn or tumbled material.
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Physical properties
Dark gray-black, fine-grained, dull to slightly glassy, with abundant vesicles and a small tan weathered/mineral-filled patch; hardness about 5–6, no obvious cleavage, typically dense but porous. The rounded shape suggests water-worn or tumbled material.
Formation & geological history
Forms when low-silica basaltic lava cools rapidly at or near Earth’s surface, trapping gas bubbles; commonly Cenozoic to modern, though basalt occurs throughout geologic time. The tan area may be alteration or an amygdule filled with iron oxides or zeolite.
Uses & applications
Used as aggregate, road material, riprap, and lightweight landscaping stone; attractive pieces may be collected, but it is not normally a jewelry gemstone.
Geological facts
Vesicles distinguish scoria from massive basalt, while very abundant large holes and low density favor scoria. It may be weakly magnetic if it contains magnetite.
Field identification & locations
Identify it by its black basaltic color, tiny holes, irregular fracture, and lack of sedimentary layering or visible large crystals; common near volcanic fields, lava flows, and cinder cones worldwide.
