The occurring among aged volcanic rocks, the cavities are usually crammed with deposits of secondary minerals launched by percolating drinking water. The glass alone varieties threads, fibres, and thin partitions between the vesicles. Rhyolite and trachyte pumices are white, andesite pumices normally yellow or brown, and pumiceous basalts (including manifest https://edenproductsltd.co.uk/2025/04/17/the-history-of-pumice-stone-from-ancient-civilisations-to-modern-day-uses/