igneous
Pumice
Pumice (Vesicular volcanic glass)
Hardness: 5-6 Mohs. Color: white, cream, or light grey. Luster: dull to pearly. Structure: vesicular (pitted with many gas bubbles/pores). Lighter than water (floats).
- Hardness
- 5-6 Mohs
- Color
- white, cream, or light grey
- Luster
- dull to pearly
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Physical properties
Hardness: 5-6 Mohs. Color: white, cream, or light grey. Luster: dull to pearly. Structure: vesicular (pitted with many gas bubbles/pores). Lighter than water (floats).
Formation & geological history
Formed during explosive volcanic eruptions when highly pressurized, gas-rich magma is ejected into the atmosphere. The rapid cooling and depressurization trap gas bubbles, creating a frothy glass structure.
Uses & applications
Used as an abrasive in cleaning products, cosmetic exfoliants, masonry (lightweight concrete), and as a filtration medium or soil conditioner in horticulture.
Geological facts
Pumice is the only rock that can float on water until it eventually becomes waterlogged and sinks. Large eruptions can create 'pumice rafts' that float across oceans for years.
Field identification & locations
Identify by its extremely lightweight, sponge-like appearance and rough texture. Commonly found in regions with explosive volcanic history like the Andes, Cascades, or Mediterranean.
