The occurring among outdated volcanic rocks, the cavities are often crammed with deposits of secondary minerals introduced by percolating water. The glass by itself forms threads, fibres, and slim partitions involving the vesicles. Rhyolite and trachyte pumices are white, andesite pumices frequently yellow or brown, and pumiceous basalts (which include https://edenproductsltd.co.uk/2025/04/17/the-history-of-pumice-stone-from-ancient-civilisations-to-modern-day-uses/