igneous
Pumice
Pumice (Vesicular Felsic Igneous Rock)
Hardness: 6 on Mohs scale (for the glass framework, though the rock easily crumbles); Color: Light grey, white, cream, or yellowish; Luster: Dull to earthy; Crystal structure: Amorphous (volcanic glass with vesicular texture); Specific gravity: Less than 1.0 (it floats on water).
- Color
- Light grey, white, cream, or yellowish
- Luster
- Dull to earthy
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Physical properties
Hardness: 6 on Mohs scale (for the glass framework, though the rock easily crumbles); Color: Light grey, white, cream, or yellowish; Luster: Dull to earthy; Crystal structure: Amorphous (volcanic glass with vesicular texture); Specific gravity: Less than 1.0 (it floats on water).
Formation & geological history
Formed from explosive volcanic eruptions where gas-rich, frothy felsic magma rapidly cools and depressurizes, trapping gas bubbles as a glass foam.
Uses & applications
Used in lightweight concrete, landscaping, abrasive soaps, pumice stones for personal care, and horticulture.
Geological facts
Pumice is one of the only rocks that can float on water due to its high porosity and trapped air bubbles.
Field identification & locations
Easily identified by its extremely low weight, pale color, and abundant small vesicles (holes). Found worldwide in volcanic regions, particularly near subduction zones and areas with recent silicic volcanism.
