igneous
Vesicular volcanic rock, likely pumice or scoria
Vesicular rhyolitic–andesitic volcanic rock; predominantly silicate glass with feldspar and possibly pyroxene
AI-generated identification · may be incorrectLight tan, porous, and fine-grained with abundant gas vesicles; likely Mohs hardness about 5–6, dull to slightly glassy luster, no obvious cleavage, and low to moderate specific gravity. The pale color favors pumice over darker scoria, but the image alone cannot distinguish them confidently.
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Physical properties
Light tan, porous, and fine-grained with abundant gas vesicles; likely Mohs hardness about 5–6, dull to slightly glassy luster, no obvious cleavage, and low to moderate specific gravity. The pale color favors pumice over darker scoria, but the image alone cannot distinguish them confidently.
Formation & geological history
Forms when gas-rich lava rapidly decompresses and cools during an explosive eruption, trapping bubbles in the solidifying magma. Its age is eruption-dependent, ranging from modern volcanic deposits to ancient volcanic sequences.
Uses & applications
Pumice is used as a lightweight abrasive, exfoliant, concrete aggregate, and horticultural medium; scoria is used for landscaping, drainage, and lightweight construction aggregate. Common pieces have little jewelry value.
Geological facts
Vesicles are frozen gas bubbles, not fossils. Pumice can float when highly vesicular, whereas denser scoria generally sinks.
Field identification & locations
Common around volcanic regions such as Iceland, Italy, Greece, Japan, the western United States, and Mexico. Field tests include very low density, abundant cavities, lack of layering, and a gritty or glassy fracture; acid testing is generally unhelpful.
