The occurring among the aged volcanic rocks, the cavities tend to be filled with deposits of secondary minerals released by percolating drinking water. The glass by itself forms threads, fibres, and skinny partitions amongst the vesicles. Rhyolite and trachyte pumices are white, andesite pumices typically yellow or brown, and pumiceous https://edenproductsltd.co.uk/2025/04/17/the-history-of-pumice-stone-from-ancient-civilisations-to-modern-day-uses/