igneous
Pumice
Pumice (Amorphous volcanic glass)
Hardness: 5-6 (but very brittle); Color: White to light grey; Luster: Pearly or dull; Structure: Highly vesicular (honeycombed with air bubbles); Specific Gravity: 0.25-0.9 (floats in water).
- Hardness
- 5-6 (but very brittle)
- Color
- White to light grey
- Luster
- Pearly or dull
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Physical properties
Hardness: 5-6 (but very brittle); Color: White to light grey; Luster: Pearly or dull; Structure: Highly vesicular (honeycombed with air bubbles); Specific Gravity: 0.25-0.9 (floats in water).
Formation & geological history
Formed during explosive volcanic eruptions when highly pressurized, gas-rich magma is ejected rapidly. The sudden depressurization causes gas bubbles to expand, freezing the rock into a frothy glass.
Uses & applications
Used in construction for lightweight concrete, in cosmetics as an abrasive exfoliant, as a stone-washing agent for denim, and in horticulture to improve soil aeration.
Geological facts
Pumice is the only rock that can float on water due to its incredible porosity. Massive 'pumice rafts' can form in the ocean after подводный volcanic eruptions, sometimes drifting for years.
Field identification & locations
Identify by its extremely lightweight feel and the presence of numerous tiny holes (vesicles). It is commonly found around volcanic arcs and active boundary zones.
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