igneous
Vesicular basalt (likely scoria)
Basaltic volcanic rock; chiefly plagioclase, pyroxene, and olivine, with possible volcanic glass
AI-generated identification · may be incorrectDark gray to black, fine-grained and strongly vesicular, with dull to slightly vitreous luster; hardness about 5–6 Mohs, no visible cleavage, and typical specific gravity around 2.4–2.9. The metallic-looking patches may be weathered iron oxides or another attached mineral, so identification from the photo is tentative.
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Physical properties
Dark gray to black, fine-grained and strongly vesicular, with dull to slightly vitreous luster; hardness about 5–6 Mohs, no visible cleavage, and typical specific gravity around 2.4–2.9. The metallic-looking patches may be weathered iron oxides or another attached mineral, so identification from the photo is tentative.
Formation & geological history
Forms when iron- and magnesium-rich basaltic lava cools rapidly near the surface, trapping gas bubbles; commonly Quaternary to modern in age around cinder cones, lava flows, and volcanic fields.
Uses & applications
Used as lightweight aggregate, landscaping stone, abrasives, and occasionally in decorative rockwork; ordinary specimens have little jewelry value.
Geological facts
Scoria is generally darker and denser than pumice because its vesicles are less abundant and the rock retains more iron-rich minerals.
Field identification & locations
Look for a black, rough, porous texture, irregular vesicles, and substantial weight; a streak test, magnetism check, and fresh break help distinguish it from slag. Common in volcanic regions worldwide, including Hawaii, Iceland, Mexico, and the western United States.
