igneous
Vesicular volcanic scoria (likely basaltic scoria)
Scoria; predominantly iron- and magnesium-rich silicate glass with plagioclase, pyroxene, and possible olivine
AI-generated identification · may be incorrectHardness about 5–6 Mohs; dark gray to reddish-brown, highly vesicular, and dull to slightly glassy. It has an irregular texture, abundant gas cavities, low density, and generally no visible cleavage; specific gravity commonly about 1.5–2.5.
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Physical properties
Hardness about 5–6 Mohs; dark gray to reddish-brown, highly vesicular, and dull to slightly glassy. It has an irregular texture, abundant gas cavities, low density, and generally no visible cleavage; specific gravity commonly about 1.5–2.5.
Formation & geological history
Forms when gas-rich basaltic lava erupts and rapidly cools, trapping bubbles in the solidifying melt. It may range from geologically recent to any age associated with volcanic activity; the image alone cannot establish a precise age.
Uses & applications
Used as lightweight aggregate, drainage and landscaping stone, abrasive material, and occasionally in decorative specimens. Usually has low collector value unless from a notable locality or exhibiting unusual color and texture.
Geological facts
Its holes are vesicles, formed by expanding volcanic gases—not weathering or fossils. The specimen’s rough, relatively dense walls favor scoria over pumice, which is typically much lighter and paler.
Field identification & locations
Identify it by its black, brown, or red vesicular volcanic texture, jagged fracture, and lack of sedimentary layering. Common around basaltic cinder cones and lava fields, including Hawaii, Iceland, Mexico, and the western United States.
