The word may be used synonymously with "volcanic ash." It truly is mined from volcanic ash deposits, or it can be produced by crushing rock pumice. Want a further cleanse? Delponte endorses spraying pumice stones with 70 per cent alcohol to be sure there is no prospect of bacterial expansion. https://edenproductsltd.co.uk/2025/04/17/the-history-of-pumice-stone-from-ancient-civilisations-to-modern-day-uses/