The happening between previous volcanic rocks, the cavities tend to be stuffed with deposits of secondary minerals launched by percolating water. The glass alone types threads, fibres, and thin partitions amongst the vesicles. Rhyolite and trachyte pumices are white, andesite pumices frequently yellow or brown, and pumiceous basalts (including occur https://edenproductsltd.co.uk/2025/04/17/the-history-of-pumice-stone-from-ancient-civilisations-to-modern-day-uses/