igneous
Pumice
Highly vesicular volcanic rock, typically rhyolitic to andesitic in composition; mainly silica-rich volcanic glass with feldspar and minor quartz or ferromagnesian minerals.
AI-generated identification · may be incorrectVery light gray, frothy, and highly porous with a dull to slightly glassy luster; hardness about 5–6 Mohs, no cleavage, and low specific gravity, often capable of floating. The cavities are gas vesicles formed during eruption.
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Physical properties
Very light gray, frothy, and highly porous with a dull to slightly glassy luster; hardness about 5–6 Mohs, no cleavage, and low specific gravity, often capable of floating. The cavities are gas vesicles formed during eruption.
Formation & geological history
Forms when gas-rich, silica-rich magma explosively erupts and cools rapidly, trapping bubbles in volcanic glass. It can form at any volcanic age; common deposits are Quaternary to recent.
Uses & applications
Used as lightweight aggregate, concrete and masonry additive, abrasive, polishing stone, horticultural soil amendment, and exfoliating material.
Geological facts
Pumice is produced during explosive eruptions and may be transported widely by wind or water as pumice rafts. Its low density distinguishes it from most other volcanic rocks.
Field identification & locations
Identify it by abundant interconnected holes, rough texture, and unusually low weight; unlike scoria, it is commonly pale gray or cream rather than dark red-brown. Common around explosive volcanic regions such as Italy, Turkey, Japan, Iceland, and the western United States.
