igneous
Pumice
Pumice, a highly vesicular volcanic glass composed mainly of rhyolitic to dacitic silicate material
AI-generated identification · may be incorrectPale gray with a dull to slightly glassy luster and abundant small pores; hardness is variable, roughly 5–6 Mohs for its glassy material. The pictured piece appears weathered, and its mineral proportions and density cannot be confirmed from the image.
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Physical properties
Pale gray with a dull to slightly glassy luster and abundant small pores; hardness is variable, roughly 5–6 Mohs for its glassy material. The pictured piece appears weathered, and its mineral proportions and density cannot be confirmed from the image.
Formation & geological history
Forms when gas-rich, silica-rich lava cools rapidly during explosive eruptions, trapping bubbles in volcanic glass. It can form at many geological ages and is commonly deposited near volcanic centers or carried offshore.
Uses & applications
Used as an abrasive, exfoliating stone, lightweight aggregate, and horticultural soil amendment; attractive pieces may be collected, but this specimen is not gem material.
Geological facts
Pumice may be so porous that it floats temporarily. The holes and irregular shape are consistent with vesicular volcanic rock, though image-only identification is uncertain.
Field identification & locations
Look for a lightweight, frothy texture with many cavities and sharp, glassy-looking edges; common sources include volcanic regions such as Italy, Iceland, Greece, and the western United States.
