Pumice is a light, porous volcanic rock that forms during explosive eruptions. It resembles a sponge because it consists of a network of gas bubbles frozen amidst fragile volcanic glass and minerals. All types of magma (basalt, andesite, dacite, and rhyolite) will form pumice.
During an explosive eruption, volcanic gases dissolved in the liquid portion of magma expand rapidly to create a foam or froth; in the case of pumice, the liquid part of the froth quickly solidifies to glass around the glass bubbles.
Our pumice is mined from a land based resource, within 50kms of Lake Taupo in the North Island of New Zealand, and it is characterized by its relative hardness and light weight in comparison to competing aggregates.