igneous
Pumice
Highly vesicular volcanic rock, typically rhyolitic to andesitic in composition
AI-generated identification · may be incorrectLight gray to tan, frothy texture with abundant interconnected vesicles; dull to slightly glassy luster, no cleavage, and generally 5–6 Mohs hardness, though fragile specimens may crumble. Its low density can allow it to float.
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Physical properties
Light gray to tan, frothy texture with abundant interconnected vesicles; dull to slightly glassy luster, no cleavage, and generally 5–6 Mohs hardness, though fragile specimens may crumble. Its low density can allow it to float.
Formation & geological history
Forms when gas-rich felsic or intermediate lava erupts and rapidly quenches, trapping bubbles in volcanic glass. It is geologically young in many deposits but occurs throughout Earth’s volcanic history.
Uses & applications
Used as an abrasive, exfoliant, lightweight aggregate, concrete additive, horticultural soil amendment, and decorative stone; collectible value is usually modest.
Geological facts
The holes are gas bubbles preserved during eruption, making pumice one of the most porous rocks. It commonly forms in explosive eruptions and may raft across oceans.
Field identification & locations
Identify it by its extremely porous, rough surface and unusually low weight; unlike vesicular basalt, it is commonly pale and may float. Common sources include volcanic regions such as Iceland, Italy, Japan, Indonesia, and the western United States.
