igneous
Pumice
Highly vesicular volcanic rock, typically rhyolitic to dacitic; mainly volcanic glass with feldspar, quartz, and mafic minerals
AI-generated identification · may be incorrectMohs hardness about 5–6; pale gray-beige, very porous, dull to silky luster, and commonly light enough to float. Lacks visible cleavage and has abundant vesicles formed by trapped gas.
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Physical properties
Mohs hardness about 5–6; pale gray-beige, very porous, dull to silky luster, and commonly light enough to float. Lacks visible cleavage and has abundant vesicles formed by trapped gas.
Formation & geological history
Forms when gas-rich felsic lava erupts explosively and cools rapidly, preserving frothy bubbles; generally Quaternary to recent, though older deposits occur worldwide.
Uses & applications
Used as an abrasive, polishing stone, lightweight aggregate, concrete additive, horticultural soil amendment, and in cosmetics; attractive pieces are collected but usually inexpensive.
Geological facts
Its extreme vesicularity distinguishes it from dense volcanic rocks; pores may become waterlogged, so some specimens eventually sink.
Field identification & locations
Identify it by its rough, hole-filled texture, low density, and gray-to-cream color; common around volcanic regions such as Iceland, Italy, Turkey, Japan, Indonesia, and the western United States.
