igneous
Pumice
Pumice; highly vesicular volcanic glass, typically rhyolitic to dacitic in composition
AI-generated identification · may be incorrectLight gray-white, extremely porous, rough, and dull to vitreous; hardness about 5–6 Mohs, with abundant small vesicles and very low density, often floating in water. It lacks well-developed crystals because it cooled rapidly as frothy volcanic glass.
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Physical properties
Light gray-white, extremely porous, rough, and dull to vitreous; hardness about 5–6 Mohs, with abundant small vesicles and very low density, often floating in water. It lacks well-developed crystals because it cooled rapidly as frothy volcanic glass.
Formation & geological history
Forms when gas-rich felsic lava erupts explosively and quenches rapidly, trapping bubbles in volcanic glass; specimens may range from modern to millions of years old. Common around explosive volcanic regions and ash deposits.
Uses & applications
Used as an abrasive, exfoliant, lightweight aggregate, horticultural additive, filtration medium, and construction material; attractive pieces are inexpensive geological specimens.
Geological facts
Its abundant interconnected pores distinguish it from denser volcanic rocks such as rhyolite. Fresh pumice can float until its pores become waterlogged.
Field identification & locations
Identify it by its unusually low weight, frothy texture, pale color, and ability to scratch softer materials; common sources include Iceland, Italy, Greece, Japan, New Zealand, and volcanic islands worldwide.
