igneous
Pumice
Pumice, vesicular volcanic glass; typically silica-rich rhyolitic composition
AI-generated identification · may be incorrectPale gray-beige, dull to slightly glassy, highly porous and lightweight, with abundant gas-bubble cavities; mostly glass with fine crystals. Hardness is variable, commonly about 5–6 Mohs, though this small rough piece cannot be identified conclusively from appearance alone.
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Physical properties
Pale gray-beige, dull to slightly glassy, highly porous and lightweight, with abundant gas-bubble cavities; mostly glass with fine crystals. Hardness is variable, commonly about 5–6 Mohs, though this small rough piece cannot be identified conclusively from appearance alone.
Formation & geological history
Forms when gas-rich, silica-rich lava cools rapidly during explosive volcanic eruptions, trapping bubbles in a frothy glass. It can form in eruptions of many ages and is found in volcanic deposits worldwide.
Uses & applications
Used as an abrasive, lightweight aggregate, and soil amendment; finer material is used in polishing and personal-care products. This small specimen has mainly educational or modest collecting value.
Geological facts
Pumice can be so vesicular that it floats temporarily. The specimen’s pale color and porous texture are consistent with pumice, though other porous volcanic rocks can look similar.
Field identification & locations
Look for a very lightweight, rough fragment riddled with irregular pores; common in volcanic regions and beach deposits near volcanoes. Estimated value: about $1–$10 for a small common specimen.
