igneous
Vesicular basalt (likely weathered scoria)
Basaltic volcanic rock; chiefly plagioclase, clinopyroxene, and iron-rich olivine, with vesicles formed by trapped gas
AI-generated identification · may be incorrectDark gray to purplish, fine-grained and strongly vesicular, with dull to weakly glassy luster; hardness about 5–6 Mohs, no obvious cleavage, and typical specific gravity around 2.4–2.9. The lavender color may reflect surface weathering, oxidation, or lighting.
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Physical properties
Dark gray to purplish, fine-grained and strongly vesicular, with dull to weakly glassy luster; hardness about 5–6 Mohs, no obvious cleavage, and typical specific gravity around 2.4–2.9. The lavender color may reflect surface weathering, oxidation, or lighting.
Formation & geological history
An extrusive igneous rock produced when basaltic lava cooled rapidly at or near Earth’s surface, commonly during Cenozoic or younger volcanic activity; its exact age cannot be determined from the photograph.
Uses & applications
Used as aggregate, road material, riprap, landscaping stone, and occasionally as a decorative or lapidary specimen; porous scoria is also used in lightweight concrete and horticulture.
Geological facts
Vesicles indicate escaping volcanic gases; irregular cavities and rough texture distinguish it from most massive basalt. It may occur in lava flows, cinder cones, volcanic bombs, and scoria deposits.
Field identification & locations
Identify it by its low density, abundant rounded or elongated gas cavities, fine texture, and dark basaltic composition; common in volcanic regions such as Iceland, Hawaii, the western United States, Italy, and Japan. A definitive identification would require density, streak, and thin-section or chemical testing.
