igneous
Vesicular volcanic rock, likely pumice or scoriaceous rhyolite
Vesicular rhyolite/dacite; predominantly silica-rich volcanic glass with feldspar and quartz
AI-generated identification · may be incorrectLight tan, highly porous, and probably lightweight, with abundant rounded to irregular vesicles and a dull earthy-to-glassy luster. Hardness is approximately 5–6 Mohs; crystals are fine-grained or partly glassy, with no obvious cleavage; exact density and composition require testing.
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Physical properties
Light tan, highly porous, and probably lightweight, with abundant rounded to irregular vesicles and a dull earthy-to-glassy luster. Hardness is approximately 5–6 Mohs; crystals are fine-grained or partly glassy, with no obvious cleavage; exact density and composition require testing.
Formation & geological history
Formed when gas-rich felsic lava or pyroclastic material rapidly cooled, trapping bubbles; likely Cenozoic, though age cannot be determined from the image. Common in volcanic fields, ash-flow deposits, and welded or non-welded tuffs.
Uses & applications
Used as lightweight aggregate, abrasives, landscaping stone, and occasionally decorative material; quality pumice may be collected, but this specimen is unlikely to have significant commercial value.
Geological facts
The large cavities are vesicles produced by expanding volcanic gases, not fossil holes. Its pale color favors pumiceous rhyolite or tuff over dark basaltic scoria.
Field identification & locations
Likely identification as pumiceous volcanic tuff can be tested by low density, abrasion, and streak: pumice may float briefly, while tuff is denser and crumbly. Common localities include the western United States, Italy, Greece, Turkey, and Japan.
