igneous
Vesicular basalt (likely scoria)
Basaltic volcanic rock; chiefly plagioclase, pyroxene, and olivine, with vesicles formed by trapped gas
AI-generated identification · may be incorrectDark brown to reddish-brown, highly vesicular, dull to slightly earthy luster, fine-grained groundmass; hardness about 5–6 Mohs, no obvious cleavage, specific gravity commonly 2.4–2.9 (lower if extremely vesicular).
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Physical properties
Dark brown to reddish-brown, highly vesicular, dull to slightly earthy luster, fine-grained groundmass; hardness about 5–6 Mohs, no obvious cleavage, specific gravity commonly 2.4–2.9 (lower if extremely vesicular).
Formation & geological history
Formed when basaltic lava cooled rapidly at or near the surface, preserving abundant gas bubbles; age depends on locality and may range from recent eruptions to hundreds of millions of years.
Uses & applications
Used as lightweight aggregate, landscaping stone, drainage material, and occasionally as an abrasive or decorative specimen; limited jewelry value.
Geological facts
The holes are vesicles, not fossils, and their shape reflects gas escape during eruption. Brown coloration commonly results from oxidation of iron-bearing minerals.
Field identification & locations
Identify by its porous volcanic texture, irregular vesicles, and lack of layering or sedimentary grains; common in volcanic regions worldwide, including Hawaii, Iceland, the western United States, and oceanic islands.
