igneous
Scoriaceous basalt (volcanic scoria)
Vesicular basalt; commonly pyroxene–plagioclase basalt with iron-rich glass
AI-generated identification · may be incorrectHardness about 5–6 Mohs; dark gray to reddish-brown, dull to slightly glassy luster, and highly vesicular texture from abundant gas bubbles. No prominent cleavage; typically low-to-moderate density, though this specimen appears relatively dense and weathered.
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Physical properties
Hardness about 5–6 Mohs; dark gray to reddish-brown, dull to slightly glassy luster, and highly vesicular texture from abundant gas bubbles. No prominent cleavage; typically low-to-moderate density, though this specimen appears relatively dense and weathered.
Formation & geological history
Forms when gas-rich basaltic lava cools rapidly, trapping vesicles; generally Quaternary to modern in volcanic fields, cinder cones, and lava flows. Exact age and locality cannot be determined from the photograph.
Uses & applications
Used as lightweight aggregate, landscaping stone, abrasive, filtration media, and sometimes decorative material; collector value is usually modest.
Geological facts
Scoria is darker, denser, and typically less frothy than pumice because it forms from mafic lava. Its cavities may later host secondary minerals such as calcite or zeolites.
Field identification & locations
Identify by abundant irregular holes, dark mafic color, rough surface, and greater heft than pumice; distinguish from slag by natural vesicles and lack of metallic droplets or industrial glass. Common worldwide near basaltic volcanoes, including Hawaii, Iceland, Mexico, and the western United States.
