igneous
Pumice
Highly vesicular volcanic rock, commonly rhyolitic to dacitic glass (SiO₂-rich volcanic material)
AI-generated identification · may be incorrectVery light gray, porous, and dull to slightly glassy, with abundant rounded vesicles; hardness about 5–6, no cleavage, irregular fracture, and typically low specific gravity, often floating in water. The holes here could also reflect weathering or minor biological boring.
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Physical properties
Very light gray, porous, and dull to slightly glassy, with abundant rounded vesicles; hardness about 5–6, no cleavage, irregular fracture, and typically low specific gravity, often floating in water. The holes here could also reflect weathering or minor biological boring.
Formation & geological history
Forms when gas-rich lava erupts explosively and rapidly cools, trapping bubbles in volcanic glass; specimens are generally geologically young, ranging from recent eruptions to Cenozoic deposits. Common around volcanic islands, beaches, and ash deposits worldwide.
Uses & applications
Used as an abrasive, exfoliant, lightweight aggregate, concrete additive, horticultural soil amendment, and decorative stone; usually little jewelry value.
Geological facts
Pumice is a frothy volcanic glass, unlike scoria, which is usually darker and more iron-rich. Its extreme vesicularity results from dissolved volcanic gases expanding during decompression.
Field identification & locations
Identify it by its unusually low density, pale color, abundant interconnected pores, and rough texture; it may float if pores are open. Common sources include Italy, Greece, Turkey, Japan, New Zealand, and volcanic beaches.
