igneous
Pumice
Pumicite (Volcanic glass with vesicular texture)
Hardness: 5-6 (but brittle), Color: Light gray/tan, Luster: Dull to silky, Structure: Vesicular/frothy glass, Specific Gravity: <1.0 (floats in water)
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Physical properties
Hardness: 5-6 (but brittle), Color: Light gray/tan, Luster: Dull to silky, Structure: Vesicular/frothy glass, Specific Gravity: <1.0 (floats in water)
Formation & geological history
Formed during explosive volcanic eruptions when highly pressurized, gas-rich molten rock (magma) is ejected and cools rapidly, trapping gas bubbles.
Uses & applications
Abrasives in cleaning and beauty products, lightweight concrete additive, landscaping, denim stone-washing, and horticulture.
Geological facts
Pumice is the only rock that floats on water until it eventually becomes waterlogged and sinks. Large 'pumice rafts' can float across oceans for years.
Field identification & locations
Identified by its extremely lightweight feel and high porosity (honeycomb appearance). Commonly found in volcanic regions like the Cascades, Italy, or Iceland.
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