igneous
Pumice
Pumice (volcanic glass foam)
AI-generated identification · may be incorrectHardness 6 on Mohs scale; light gray to white color; vitreous to dull luster; amorphous 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 color; vitreous to dull luster; amorphous glass structure; specific gravity less than 1.0, allowing it to float on water.
Formation & geological history
Formed from explosive volcanic eruptions where frothy, gas-rich dacitic or rhyolitic lava rapidly cools and depressurizes, trapping gas bubbles.
Uses & applications
Used widely in lightweight concrete aggregates, abrasive personal care products, stonewashing denim, and horticultural soil amendments.
Geological facts
Pumice is one of the few geological materials that can float on water due to its extreme vesicular porosity. Major deposits occur globally in regions with active or recent subduction-zone volcanism.
Field identification & locations
Easily identified in the field by its exceptionally low weight-to-size ratio and visible micro-vesicular texture resembling a hardened sponge. Found near volcanic arcs worldwide.
