igneous
Vesicular basalt (likely weathered scoria)
Vesicular mafic volcanic rock, chiefly plagioclase, pyroxene, and volcanic glass; commonly ~45–52% SiO₂
AI-generated identification · may be incorrectDark gray to black, fine-grained, highly vesicular, with dull to submetallic weathered surfaces; hardness about 5–6, no visible cleavage, and typical specific gravity ~2.4–2.9. The cavities are gas bubbles, not crystal faces.
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Physical properties
Dark gray to black, fine-grained, highly vesicular, with dull to submetallic weathered surfaces; hardness about 5–6, no visible cleavage, and typical specific gravity ~2.4–2.9. The cavities are gas bubbles, not crystal faces.
Formation & geological history
Formed when basaltic lava cooled rapidly at or near the surface, trapping volcanic gases; the specimen’s exact age and locality cannot be determined from the image. Weathering has rounded and altered the surface.
Uses & applications
Used as lightweight aggregate, landscaping stone, road material, abrasive, and sometimes decorative rock; usually low-value as a hand specimen.
Geological facts
Scoria is generally more vesicular and lighter than ordinary basalt, while denser vesicular basalt may sink in water. Some cavities can later host zeolite, calcite, or quartz minerals.
Field identification & locations
Look for a dark fine-grained matrix, abundant irregular holes, and a relatively heavy feel; distinguish it from pumice because basaltic scoria is darker and generally denser. Common in volcanic fields, lava flows, and cinder cones worldwide.
