igneous
Vesicular volcanic scoria (likely basaltic scoria)
Scoria; predominantly vesicular basalt, composed mainly of plagioclase, pyroxene, and iron-rich glass
AI-generated identification · may be incorrectHardness about 5–6 Mohs; dark gray to reddish-brown, rough, dull to slightly glassy, and extremely porous with abundant gas vesicles. It has no obvious cleavage and low-to-moderate density, though the pale weathered surface may reflect alteration or mineral coating.
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Physical properties
Hardness about 5–6 Mohs; dark gray to reddish-brown, rough, dull to slightly glassy, and extremely porous with abundant gas vesicles. It has no obvious cleavage and low-to-moderate density, though the pale weathered surface may reflect alteration or mineral coating.
Formation & geological history
Forms when gas-rich basaltic lava cools rapidly, trapping bubbles during an eruption; commonly Quaternary to modern in age. The specimen may also be weathered or partially mineralized after formation.
Uses & applications
Used as lightweight aggregate, drainage material, landscaping stone, abrasive, and occasionally in cement or horticulture; generally not used as a gemstone.
Geological facts
Scoria is denser and typically darker than pumice, whose vesicles are more abundant and whose walls are often glassier. Its irregular cavities are volcanic gas bubbles rather than fossils.
Field identification & locations
Identify it by its highly vesicular texture, angular cavities, rough surface, and volcanic appearance; common around cinder cones, lava flows, and basaltic volcanoes worldwide. Estimated value: $5–$25 for a common hand specimen, or up to $50 for an unusually large or attractive piece.
