igneous
Vesicular volcanic rock, likely pumice or scoriaceous rhyolite
Silica-rich vesicular volcanic rock; commonly rhyolitic pumice (SiO₂-rich glass)
AI-generated identification · may be incorrectLight tan-pink, highly porous, dull to slightly glassy, with abundant gas cavities and dark mineral fragments; hardness about 5–6 for rhyolitic material, with no obvious cleavage and low specific gravity. The specimen appears denser and more lithic than typical pumice, so it may be weathered scoria or welded tuff.
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Physical properties
Light tan-pink, highly porous, dull to slightly glassy, with abundant gas cavities and dark mineral fragments; hardness about 5–6 for rhyolitic material, with no obvious cleavage and low specific gravity. The specimen appears denser and more lithic than typical pumice, so it may be weathered scoria or welded tuff.
Formation & geological history
Formed when gas-rich volcanic magma erupted explosively and rapidly cooled, trapping bubbles in volcanic glass; likely Quaternary to older Cenozoic, depending on locality. Vesicular textures commonly occur in ash-flow deposits, lava domes, and pyroclastic ejecta.
Uses & applications
Used as lightweight aggregate, abrasive, landscaping stone, and cement additive; attractive pieces are collected but this specimen has modest jewelry value.
Geological facts
The holes are vesicles formed by expanding volcanic gases, not biological pores. Dark streaks may represent iron-rich minerals or compressed volcanic material.
Field identification & locations
Identify it by its low density, porous texture, irregular fracture, and volcanic appearance; pumice may float briefly, whereas denser scoria or tuff sinks. Common worldwide in volcanic regions, including Italy, Iceland, Mexico, and the western United States.
