igneous
Likely vesicular basalt (scoria)
Basaltic scoria; chiefly plagioclase, pyroxene, and olivine with volcanic glass
AI-generated identification · may be incorrectDark gray to black, rough and highly vesicular, with dull to subvitreous luster; hardness about 5–6 Mohs and no consistent cleavage. The apparent metallic-looking flecks may be reflective crystal faces or coating; scale suggests a small hand specimen.
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Physical properties
Dark gray to black, rough and highly vesicular, with dull to subvitreous luster; hardness about 5–6 Mohs and no consistent cleavage. The apparent metallic-looking flecks may be reflective crystal faces or coating; scale suggests a small hand specimen.
Formation & geological history
An extrusive volcanic rock formed when gas-rich basaltic lava cooled rapidly, trapping bubbles; commonly Quaternary to Recent, though basaltic scoria occurs throughout geologic time.
Uses & applications
Used as lightweight aggregate, landscaping stone, drainage material, and abrasive; attractive pieces are sold as volcanic-rock specimens, but this small example has little commercial value.
Geological facts
Scoria is denser and generally darker than pumice, whose abundant interconnected pores often make it float. A magnet test may detect minor iron-bearing minerals, but it is not diagnostic.
Field identification & locations
Common around cinder cones, lava flows, and volcanic fields worldwide, including Hawaii, Iceland, Mexico, and the western United States. Confirm with abundant irregular pores, a black basaltic matrix, and lack of uniform manufactured texture; exact identification requires fresh surface or testing.
