igneous
Pumice
Pumice, a highly vesicular volcanic rock composed mainly of volcanic glass with variable feldspar and silica minerals
AI-generated identification · may be incorrectLight tan, porous, and dull to silky; its cavities (vesicles) formed as gas escaped from cooling lava. Hardness varies, typically about 5–6 Mohs for the glassy material; crystal structure is largely amorphous.
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Physical properties
Light tan, porous, and dull to silky; its cavities (vesicles) formed as gas escaped from cooling lava. Hardness varies, typically about 5–6 Mohs for the glassy material; crystal structure is largely amorphous.
Formation & geological history
Forms when gas-rich, silica-rich lava cools and depressurizes rapidly during explosive eruptions. It is geologically young volcanic material, though the specimen’s age and exact source cannot be determined from the image.
Uses & applications
Used as an abrasive, lightweight aggregate, and soil amendment; finer or shaped material is also used for cosmetic exfoliation and polishing.
Geological facts
Pumice is so full of gas bubbles that many pieces can float temporarily on water.
Field identification & locations
Look for a very lightweight, frothy rock with abundant interconnected pores and sharp, glassy surfaces. Common around explosive volcanoes, including in Italy, Iceland, and the western United States.
