igneous
Pumice
Pumice (volcanic glass rock)
Hardness: 5-6 (Mohs), Color: white, cream, or light grey, Luster: dull to pearly, Structure: vesicular (highly porous/holey), Specific Gravity: 0.25 to 0.7 (floats in water)
Identified More igneous →
Explore Pumice in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness: 5-6 (Mohs), Color: white, cream, or light grey, Luster: dull to pearly, Structure: vesicular (highly porous/holey), Specific Gravity: 0.25 to 0.7 (floats in water)
Formation & geological history
Formed during explosive volcanic eruptions when highly pressurized, gas-rich magma is ejected. The rapid cooling and depressurization trap gas bubbles as the rock solidifies.
Uses & applications
Used as an abrasive in polishing, personal care (exfoliation), lightweight concrete aggregate, horticultural soil amendments, and stonewashed jeans production.
Geological facts
Pumice is the only rock that can float on water until it eventually becomes waterlogged and sinks. Large rafts of floating pumice can drift across oceans for years after an eruption.
Field identification & locations
Identify by its extremely lightweight feel, porous and frothy appearance, and ability to float in water. Commonly found in volcanic regions like the Cascades, Andes, and Mediterranean.
