The phrase can be used synonymously with "volcanic ash." It can be mined from volcanic ash deposits, or it can be produced by crushing rock pumice. Due to its porous structure, pumice is Utilized in soil mixes for horticulture. It helps with water retention, aeration, and drainage in potting soils https://edenproductsltd.co.uk/2025/04/17/the-history-of-pumice-stone-from-ancient-civilisations-to-modern-day-uses/