igneous
Vesicular volcanic rock, likely scoria
Scoria (vesicular basaltic-andesitic rock), composed mainly of plagioclase, pyroxene, and volcanic glass
AI-generated identification · may be incorrectDark reddish-brown, highly vesicular, rough, dull to weakly vitreous surface; typically hardness 5–6 Mohs, no consistent cleavage, and specific gravity about 2.0–2.8. The prominent cavity is a gas bubble mold; iron oxidation produces the red-brown color.
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Physical properties
Dark reddish-brown, highly vesicular, rough, dull to weakly vitreous surface; typically hardness 5–6 Mohs, no consistent cleavage, and specific gravity about 2.0–2.8. The prominent cavity is a gas bubble mold; iron oxidation produces the red-brown color.
Formation & geological history
Forms when gas-rich basaltic or andesitic lava rapidly cools, trapping bubbles; commonly Quaternary to Recent in volcanic cones, lava flows, and cinder deposits. The specimen may also be weathered vesicular basalt rather than true scoria.
Uses & applications
Used as lightweight aggregate, drainage material, landscaping stone, abrasive, and occasionally decorative material; generally not used as a gemstone.
Geological facts
Scoria is denser and darker than pumice, which is usually pale and may float. Vesicles can later become lined or filled with secondary minerals such as zeolites, calcite, or quartz.
Field identification & locations
Identify by abundant irregular holes, reddish oxidation, rough texture, and volcanic appearance; common worldwide near basaltic volcanoes, including Hawaii, Iceland, Italy, Mexico, and the western United States. A precise identification would benefit from density and thin-section testing.
