igneous
Vesicular basalt (likely scoria)
Basaltic volcanic rock, chiefly plagioclase, pyroxene, and often olivine
AI-generated identification · may be incorrectGray-brown, fine-grained, dull to slightly glassy, with rounded gas vesicles; hardness about 5–6 Mohs and generally no visible cleavage. Low density relative to dense basalt; the holes are natural bubbles rather than drilled openings.
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Physical properties
Gray-brown, fine-grained, dull to slightly glassy, with rounded gas vesicles; hardness about 5–6 Mohs and generally no visible cleavage. Low density relative to dense basalt; the holes are natural bubbles rather than drilled openings.
Formation & geological history
Formed when gas-rich basaltic lava cooled rapidly at or near the surface, commonly during Cenozoic or younger volcanic eruptions. Exact age cannot be determined from the image.
Uses & applications
Used as lightweight aggregate, landscaping stone, drainage material, and occasionally as a specimen or abrasive. Vesicular basalt is generally not used for fine jewelry.
Geological facts
The specimen resembles scoria, though its relatively pale, compact appearance could also represent weathered vesicular basalt. Vesicles may later become filled with zeolite, calcite, or quartz.
Field identification & locations
Common in volcanic regions such as Hawaii, Iceland, the western United States, Mexico, and the Mediterranean. Identify it by its dark volcanic matrix, bubble-like cavities, irregular shape, and lack of sedimentary layering; confirm with a fresh surface and density test.
