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