igneous
Pumice
Pumice (Vesicular Felsic to Intermediate Volcanic Rock)
Hardness: 6 on the Mohs scale; Color: White, grey, yellowish, brown, or pink; Luster: Dull to earthy; Crystal structure: Amorphous (glassy volcanic rock, lacks a true crystal structure); Cleavage: None; Specific gravity: Extremely low (typically less than 1.0, allowing it to float on water).
- Hardness
- 6 on the Mohs scale
- Color
- White, grey, yellowish, brown, or pink
- Luster
- Dull to earthy
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Physical properties
Hardness: 6 on the Mohs scale; Color: White, grey, yellowish, brown, or pink; Luster: Dull to earthy; Crystal structure: Amorphous (glassy volcanic rock, lacks a true crystal structure); Cleavage: None; Specific gravity: Extremely low (typically less than 1.0, allowing it to float on water).
Formation & geological history
Formed through explosive volcanic eruptions where gas-rich, felsic to intermediate magma cools so rapidly that gas bubbles are trapped inside the glass matrix before it can crystallize. Common in volcanic regions worldwide.
Uses & applications
Used in lightweight construction materials (concrete and cinder blocks), abrasive agents in personal care products (pumice stones, exfoliating scrubs), horticulture (soil aeration and drainage), and stonewashing denim.
Geological facts
Pumice is one of the very few rocks that can float on water due to its high porosity and trapped air bubbles. It has been used since ancient times for polishing and body care.
Field identification & locations
Easily identified in the field by its very light weight, sponge-like vesicular texture full of holes, and ability to float on water. Commonly found near active or ancient volcanic zones.
