igneous
Vesicular basalt (scoria)
Basaltic scoria; chiefly plagioclase, clinopyroxene, olivine, and volcanic glass
AI-generated identification · may be incorrectDark brown to black, highly vesicular, rough, and lightweight with dull to slightly glassy luster; hardness about 5–6 Mohs, no prominent cleavage, and fine-grained groundmass. The reddish-brown color commonly reflects oxidation of iron minerals.
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Physical properties
Dark brown to black, highly vesicular, rough, and lightweight with dull to slightly glassy luster; hardness about 5–6 Mohs, no prominent cleavage, and fine-grained groundmass. The reddish-brown color commonly reflects oxidation of iron minerals.
Formation & geological history
An extrusive igneous rock formed when gas-rich basaltic lava cools rapidly, trapping bubbles; typically Quaternary to modern in volcanic cones, lava flows, and cinder deposits. The image alone cannot establish a precise age or locality.
Uses & applications
Used as lightweight aggregate, drainage and landscaping stone, abrasive material, and sometimes in barbecue or horticultural applications; less commonly collected as a volcanic specimen.
Geological facts
Its abundant holes are vesicles formed by escaping water vapor and carbon dioxide. Scoria is generally denser and darker than pumice, which is usually pale and can float.
Field identification & locations
Identify it by its dark basaltic color, abundant irregular cavities, rough texture, and weak magnetism; common around basaltic volcanoes and cinder cones. A fresh broken surface and a magnet test help distinguish it from industrial slag.
