igneous
Vesicular basalt (likely scoria)
Basaltic volcanic rock; mainly plagioclase, pyroxene, and often olivine, with abundant gas vesicles
AI-generated identification · may be incorrectDark gray to black, rough and highly vesicular, with dull to subvitreous luster; hardness about 5–6 Mohs, fine-grained, and typically massive without cleavage. The specimen appears porous and irregular, though its surface is partly weathered or coated.
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Physical properties
Dark gray to black, rough and highly vesicular, with dull to subvitreous luster; hardness about 5–6 Mohs, fine-grained, and typically massive without cleavage. The specimen appears porous and irregular, though its surface is partly weathered or coated.
Formation & geological history
Forms when basaltic lava or pyroclastic material cools rapidly at or near the surface, trapping volcanic gas bubbles; commonly Cenozoic to modern, depending on locality. The image alone cannot establish its exact age or whether it is scoria versus dense vesicular basalt.
Uses & applications
Used as lightweight aggregate, landscaping stone, abrasive, drainage material, and occasionally in decorative specimens; generally not used as a gemstone.
Geological facts
Scoria is typically more vesicular and lighter than ordinary basalt, while pumice is usually much lighter in color and may float. A streak, density test, and fresh broken surface help distinguish it from industrial slag.
Field identification & locations
Common in volcanic fields, lava flows, cinder cones, and volcanic beaches worldwide, including Hawaii, Iceland, Mexico, and the western United States. Look for natural vesicles, crystalline grains, and absence of glassy flow textures or metallic inclusions.
