igneous
Scoria
Vesicular basaltic scoria; chiefly plagioclase, pyroxene, olivine, and volcanic glass
AI-generated identification · may be incorrectDark reddish-brown, highly vesicular, rough, and glassy to dull; typically Mohs 5–6, with no visible cleavage and low-to-moderate specific gravity due to abundant gas cavities.
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Physical properties
Dark reddish-brown, highly vesicular, rough, and glassy to dull; typically Mohs 5–6, with no visible cleavage and low-to-moderate specific gravity due to abundant gas cavities.
Formation & geological history
An extrusive volcanic rock formed when gas-rich basaltic magma erupts and rapidly cools, trapping bubbles; commonly Quaternary to Recent, though older examples occur in volcanic fields.
Uses & applications
Used as lightweight aggregate, landscaping stone, drainage material, and decorative rock; generally has little gem or collector value.
Geological facts
Its red color commonly results from oxidation of iron-bearing minerals during or after eruption. It differs from pumice because scoria is darker, denser, and basaltic rather than usually pale and silica-rich.
Field identification & locations
Identify it by its black, brown, or red color, abundant irregular vesicles, rough texture, and ability to feel relatively lightweight; common around cinder cones and basaltic volcanoes worldwide, including Hawaii, Iceland, Mexico, and the western United States.
