igneous
Vesicular basalt (likely scoria)
Basaltic volcanic rock; primarily plagioclase, clinopyroxene, olivine, and volcanic glass
AI-generated identification · may be incorrectDark gray to brown, highly vesicular, dull to slightly glassy luster; hardness about 5–6, generally massive with no cleavage, and specific gravity commonly 2.2–2.8 because of abundant gas cavities.
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Physical properties
Dark gray to brown, highly vesicular, dull to slightly glassy luster; hardness about 5–6, generally massive with no cleavage, and specific gravity commonly 2.2–2.8 because of abundant gas cavities.
Formation & geological history
Formed when basaltic lava cooled rapidly at or near Earth’s surface, trapping expanding gas bubbles; specimens may range from ancient volcanic rocks to modern eruptions, so age cannot be determined visually.
Uses & applications
Used as lightweight aggregate, landscaping stone, abrasive material, and occasionally in construction; usually has little jewelry value, though attractive vesicular pieces are collected.
Geological facts
The holes are vesicles formed by escaping volcanic gases, and their abundance indicates eruption or cooling conditions rather than weathering alone.
Field identification & locations
Identify it by its dark, fine-grained matrix and numerous irregular cavities; common in volcanic regions such as Hawaii, Iceland, the Azores, Japan, and the western United States. The image is consistent with vesicular basalt, but its pale weathered coating makes exact identification uncertain.
