igneous
Pumice
Vesicular volcanic glass, typically rhyolitic to dacitic in composition
AI-generated identification · may be incorrectVery light gray, highly porous, dull to silky luster, and commonly floats in water; hardness about 5–6 Mohs, with no visible crystal cleavage. The holes are gas vesicles preserved in rapidly cooled volcanic glass.
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Physical properties
Very light gray, highly porous, dull to silky luster, and commonly floats in water; hardness about 5–6 Mohs, with no visible crystal cleavage. The holes are gas vesicles preserved in rapidly cooled volcanic glass.
Formation & geological history
Forms when gas-rich lava erupts explosively and cools so quickly that bubbles remain trapped; most specimens are geologically young, ranging from Holocene to older Cenozoic volcanic deposits.
Uses & applications
Used as an abrasive, exfoliant, lightweight aggregate, horticultural soil additive, and cement additive; attractive pieces are inexpensive curios and craft materials.
Geological facts
Pumice is often confused with scoria, but pumice is generally lighter-colored and more silica-rich, while scoria is darker and denser.
Field identification & locations
Identify it by its frothy texture, sharp irregular pores, pale color, and unusually low density; common around volcanic regions and beaches receiving volcanic debris. The pictured specimen appears consistent with pumice, though small image size limits certainty.
