igneous
Pumice
Pumice (a frothy volcanic glass)
Hardness: 5-6 (but very brittle); Color: Light gray, white, or cream; Luster: Dull to pearly; Crystal structure: Amorphous/Vesicular; Specific Gravity: 0.25-1.2 (floats in water).
- Hardness
- 5-6 (but very brittle)
- Color
- Light gray, white, or cream
- Luster
- Dull to pearly
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 (but very brittle); Color: Light gray, white, or cream; Luster: Dull to pearly; Crystal structure: Amorphous/Vesicular; Specific Gravity: 0.25-1.2 (floats in water).
Formation & geological history
Formed during explosive volcanic eruptions when pressurized liquid rock is violently ejected. The rapid cooling and depressurization cause gas bubbles to expand, creating a porous, frothy texture.
Uses & applications
Used as an abrasive in cleaning products, cosmetic exfoliants (lava soaps/foot scrubs), construction (lightweight concrete), and horticulture (soil aeration).
Geological facts
Pumice is the only rock that floats on water. Massive 'pumice rafts' can form after submarine eruptions, floating for thousands of miles across oceans.
Field identification & locations
Identify by its extremely light weight, rough/scratchy feel, and visible small holes (vesicles). Found in volcanic regions like Italy, Turkey, Greece, and the Western USA.
