igneous
Vesicular basalt (likely weathered volcanic scoria)
Basaltic scoria; primarily plagioclase, pyroxene, and olivine
AI-generated identification · may be incorrectDark gray-brown, highly vesicular, dull to slightly glassy luster; typically hardness 5–6 Mohs, no obvious cleavage, and specific gravity about 2.4–2.8 (lower when porous). The pale/yellow patches may be weathering products or mineral coatings.
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Physical properties
Dark gray-brown, highly vesicular, dull to slightly glassy luster; typically hardness 5–6 Mohs, no obvious cleavage, and specific gravity about 2.4–2.8 (lower when porous). The pale/yellow patches may be weathering products or mineral coatings.
Formation & geological history
Formed when gas-rich basaltic lava cooled rapidly, trapping bubbles; likely Cenozoic or younger, though age cannot be determined visually. Common in volcanic cones, lava flows, and cinder deposits.
Uses & applications
Used as lightweight aggregate, landscaping stone, abrasive, and occasionally in decorative collections; generally not a jewelry gemstone.
Geological facts
Its holes are vesicles formed by expanding volcanic gases, distinguishing scoria from dense basalt. A yellow coating could indicate iron oxides, sulfur-bearing alteration, or another secondary mineral.
Field identification & locations
Look for a lightweight, rough, dark volcanic rock with abundant rounded cavities and uneven edges; common worldwide near basaltic volcanoes, including Hawaii, Iceland, Mexico, and the western United States. A magnet or hardness test may help, but laboratory analysis is needed for certainty.
