igneous
Pumice
Pumice (Felsic volcanic glass)
Hardness: 5-6 (Mohs scale), Color: Light gray to off-white, Luster: Dull to earthy, Texture: Highly vesicular (porous) with cellular structure, Specific gravity: 0.25-0.9 (floats on 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 scale), Color: Light gray to off-white, Luster: Dull to earthy, Texture: Highly vesicular (porous) with cellular structure, Specific gravity: 0.25-0.9 (floats on water)
Formation & geological history
Formed during explosive volcanic eruptions when highly gas-saturated, silicic magma cools extremely rapidly, trapping gas bubbles in a frothy glass matrix.
Uses & applications
Used as an abrasive in polishing, skin care (pumice stones), lightweight aggregate in concrete, soil conditioner in horticulture, and denim washing.
Geological facts
Pumice is the only rock that can float on water due to its extremely low density and interconnected gas pockets. Massive pumice rafts can drift across oceans for thousands of miles following volcanic eruptions.
Field identification & locations
Identified by its extremely lightweight feel, light color, and porous, sponge-like texture. Common in areas with explosive volcanic history, riverbeds downstream from volcanoes, and coastal beach deposits.
