PUMICE IS BORN in pyroclasic events, typically spewed as ash that falls and drifts into deposits or as part of a massive pyroclastic flow. Many factors affect the useful quality, color, and purity of a pumice deposit, but on a chemical analysis level, pumice is basically an aluminum silicate. With no crystalline structure, pumice is a naturally calcined amorphous glass made up of a maze of air-filled vesicles.
Pumice made its mark in history as being of value to industry when Roman engineers combined pumice aggregate and fine-grained pumice (a pozzolan) with their hydrated lime cement to make a lightweight, enduring concrete. Today, pumice is still being used as a superior pozzolan to super-charge concrete, but is also used widely in a variety of industrial process and product applications.
Pumice enjoys a well-deserved green credibility, as it is an abundant and sustainable resource, easily mined from surface deposits, and by virtue of being naturally calcined in the fiery heat of a volcano, the only refining needed is to crush it to grade.