igneous
Likely weathered vesicular volcanic rock
Probable basaltic scoria or vesicular andesite; exact identification requires testing
AI-generated identification · may be incorrectGray-brown, rounded, fine-grained stone with small cavities (vesicles) and dull to faintly glassy luster. Estimated hardness 5–6 Mohs; crystals are too fine to resolve, and cleavage is absent; relatively low to moderate specific gravity depending on vesicle volume.
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Physical properties
Gray-brown, rounded, fine-grained stone with small cavities (vesicles) and dull to faintly glassy luster. Estimated hardness 5–6 Mohs; crystals are too fine to resolve, and cleavage is absent; relatively low to moderate specific gravity depending on vesicle volume.
Formation & geological history
Formed when gas-rich lava cooled rapidly, trapping bubbles in the solidifying rock; likely Cenozoic or younger, though age cannot be determined visually. Surface rounding suggests stream, beach, or glacial transport and weathering.
Uses & applications
Commonly used as lightweight aggregate, landscaping stone, and occasionally abrasive material; generally has little jewelry value.
Geological facts
The cavities are frozen gas bubbles, not fossil holes. A magnetic response may occur if the rock is iron-rich basaltic material.
Field identification & locations
Look for vesicles, a fine volcanic texture, no obvious layering, and possible attraction to a magnet; a streak, density test, and fresh broken surface would improve identification. Common in volcanic regions worldwide, including Hawaii, Iceland, the western United States, and Japan.
