The developing amid old volcanic rocks, the cavities tend to be filled with deposits of secondary minerals launched by percolating drinking water. The glass by itself kinds threads, fibres, and thin partitions in between the vesicles. Rhyolite and trachyte pumices are white, andesite pumices usually yellow or brown, and pumiceous https://edenproductsltd.co.uk/2025/04/17/the-history-of-pumice-stone-from-ancient-civilisations-to-modern-day-uses/