igneous
Pumice
Pumice (volcanic glass with vesicular texture)
Hardness: 5-6 (Mohs scale), though prone to crumbling; Color: Cream, light gray, or tan; Luster: Dull to pearly; Structure: Amorphous/Vesicular (porous); Specific Gravity: 0.25-0.9 (often floats on water).
- Hardness
- 5-6 (Mohs scale), though prone to crumbling
- Color
- Cream, light gray, or tan
- Luster
- Dull to pearly
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Physical properties
Hardness: 5-6 (Mohs scale), though prone to crumbling; Color: Cream, light gray, or tan; Luster: Dull to pearly; Structure: Amorphous/Vesicular (porous); Specific Gravity: 0.25-0.9 (often floats on water).
Formation & geological history
Formed during explosive volcanic eruptions when highly pressurized, gas-rich rhyolitic or dacitic lava cools rapidly, trapping gas bubbles (vesicles) as the pressure drops suddenly.
Uses & applications
Used as an abrasive in skincare (exfoliation), heavy-duty cleaning, stonewashed denim production, and as a lightweight aggregate in concrete and landscaping.
Geological facts
Pumice is the only rock that can float on water due to its air-filled pores. Large eruptions can create 'pumice rafts' that drift across oceans for years and can even be seen from space.
Field identification & locations
Identify in the field by its sponge-like appearance and surprisingly light weight. It is commonly found near volcanic arcs and active or dormant explosive volcanoes like those in Italy, Turkey, and the USA.
