The transpiring amid old volcanic rocks, the cavities are usually stuffed with deposits of secondary minerals released by percolating h2o. The glass itself sorts threads, fibres, and thin partitions between the vesicles. Rhyolite and trachyte pumices are white, andesite pumices typically yellow or brown, and pumiceous basalts (for example come https://edenproductsltd.co.uk/2025/04/17/the-history-of-pumice-stone-from-ancient-civilisations-to-modern-day-uses/