The transpiring amongst outdated volcanic rocks, the cavities are frequently stuffed with deposits of secondary minerals released by percolating water. The glass alone types threads, fibres, and slender partitions between the vesicles. Rhyolite and trachyte pumices are white, andesite pumices typically yellow or brown, and pumiceous basalts (for instance come https://edenproductsltd.co.uk/2025/04/17/the-history-of-pumice-stone-from-ancient-civilisations-to-modern-day-uses/