igneous
Pumice
Pumice (SiO2)
AI-generated identification · may be incorrectHardness: 6 (can scratch glass but is very brittle); Color: light colored, usually white, light gray, or tan; Luster: dull, earthy; Crystal structure: amorphous (glassy); Cleavage: none; Specific gravity: <1 (floats on water)
- Hardness
- 6 (can scratch glass but is very brittle)
- Color
- light colored, usually white, light gray, or tan
- Luster
- dull, earthy
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Physical properties
Hardness: 6 (can scratch glass but is very brittle); Color: light colored, usually white, light gray, or tan; Luster: dull, earthy; Crystal structure: amorphous (glassy); Cleavage: none; Specific gravity: <1 (floats on water)
Formation & geological history
Formed during explosive volcanic eruptions when highly pressurized, gas-rich magma is ejected and rapidly cools and depressurizes, trapping gas bubbles (vesicles) within the volcanic glass.
Uses & applications
Used extensively as a lightweight aggregate in concrete, breeze blocks, and landscaping. Also used as an abrasive in polishes, pencil erasers, and for personal care (pumice stones).
Geological facts
Pumice is the only rock that floats on water. Massive rafts of pumice can form in the ocean after underwater volcanic eruptions and can float for years before becoming waterlogged and sinking.
Field identification & locations
Identified by its highly vesicular (bubbly) texture, light color, and extremely light weight. It will easily float on water. Commonly found in volcanic regions.
