igneous
Pumice
Pumice (volcanic glass foam)
AI-generated identification · may be incorrectHardness 6 on Mohs scale; light gray to white or yellowish; vitreous to dull luster; amorphous volcanic glass structure; specific gravity less than 1.0, allowing it to float on water.
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Physical properties
Hardness 6 on Mohs scale; light gray to white or yellowish; vitreous to dull luster; amorphous volcanic glass structure; specific gravity less than 1.0, allowing it to float on water.
Formation & geological history
Formed through the rapid cooling and depressurization of frothy, gas-rich felsic lava during explosive volcanic eruptions.
Uses & applications
Widely used in lightweight concrete aggregates, abrasive personal care products, horticultural soil amendments, and stonewashing denim.
Geological facts
Due to trapped gas bubbles expanding during eruption, pumice has a remarkably high porosity and is the only known rock that can float in water.
Field identification & locations
Easily identified by its extremely low density, vesicular texture riddled with tiny bubble cavities, and abrasive feel. Found worldwide near active or ancient subduction zone volcanoes.
