igneous
Scoria (vesicular volcanic rock)
Basaltic scoria; primarily plagioclase, pyroxene, olivine, and volcanic glass
AI-generated identification · may be incorrectDark gray-brown, highly vesicular, dull to slightly glassy, with irregular cavities; typically 5–6 on the Mohs scale, no obvious cleavage, and relatively low density (about 1–2 g/cm³). The specimen appears weathered and possibly iron-stained.
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Physical properties
Dark gray-brown, highly vesicular, dull to slightly glassy, with irregular cavities; typically 5–6 on the Mohs scale, no obvious cleavage, and relatively low density (about 1–2 g/cm³). The specimen appears weathered and possibly iron-stained.
Formation & geological history
Forms when gas-rich basaltic magma erupts and rapidly cools, trapping bubbles in the lava; most examples are geologically young, commonly Cenozoic to Recent. It occurs in cinder cones, lava flows, and volcanic fields.
Uses & applications
Used as lightweight aggregate, drainage and landscaping stone, abrasive material, and sometimes decorative rock; generally not used as a gemstone.
Geological facts
Scoria is denser and usually darker than pumice, often sinking in water, while pumice may float. Its vesicles record gases escaping during an explosive or fountaining eruption.
Field identification & locations
Identify it by its dark color, abundant interconnected-looking holes, rough surface, and volcanic texture; common worldwide near basaltic volcanoes, including Hawaii, Iceland, Italy, Mexico, and the western United States.
