igneous
Pumice
Pumice (Volcanic Rock / Glass Froth)
Hardness: 6 on the Mohs scale; Color: White, grey, yellowish, or brown; Luster: Earthy to silky; Crystal structure: Amorphous (volcanic glass with vesicular texture); Specific gravity: Less than 1.0 (floats on water).
- Hardness
- 6 on the Mohs scale
- Color
- White, grey, yellowish, or brown
- Luster
- Earthy to silky
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Physical properties
Hardness: 6 on the Mohs scale; Color: White, grey, yellowish, or brown; Luster: Earthy to silky; Crystal structure: Amorphous (volcanic glass with vesicular texture); Specific gravity: Less than 1.0 (floats on water).
Formation & geological history
Formed from explosive volcanic eruptions where gas-rich felsic or intermediate lava rapidly depressurizes and cools, trapping gas bubbles within the glassy matrix.
Uses & applications
Used in lightweight construction materials, concrete additive, abrasive in personal care products, stone-washing textiles, and horticulture.
Geological facts
Pumice is one of the few rocks that can float on water due to its high porosity and trapped gas bubbles. It has been used since antiquity for exfoliating skin and as an abrasive.
Field identification & locations
Easily identified by its extremely low density, light weight, pale color, and vesicular (sponge-like) texture. Found near young volcanic regions worldwide.
