igneous
Pumice
Pumice (Volcanic Glass)
Hardness: 6 on Mohs scale; Color: White, grey, yellowish, brown; Luster: Earthy to silky; Crystal structure: Amorphous (volcanic glass foam); Specific gravity: Less than 1.0 (floats on water due to high porosity)
- Hardness
- 6 on Mohs scale
- Color
- White, grey, yellowish, brown
- Luster
- Earthy to silky
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Physical properties
Hardness: 6 on Mohs scale; Color: White, grey, yellowish, brown; Luster: Earthy to silky; Crystal structure: Amorphous (volcanic glass foam); Specific gravity: Less than 1.0 (floats on water due to high porosity)
Formation & geological history
Formed from the explosive eruption of silica-rich volcanoes, where gas-saturated liquid magma rapidly depressurizes and cools, trapping gas bubbles within the glass matrix.
Uses & applications
Used in lightweight construction materials, concrete additive, abrasive in personal care products (pumice stones), horticulture, and polishing agents.
Geological facts
Pumice is one of the very few rocks that can float on water because of its vesicular, bubble-filled structure.
Field identification & locations
Easily identified by its extremely low weight, pale color, and numerous tiny air bubble cavities. Found globally near active or historic volcanic regions.
