The taking place amongst aged volcanic rocks, the cavities tend to be full of deposits of secondary minerals launched by percolating water. The glass itself sorts threads, fibres, and skinny partitions concerning the vesicles. Rhyolite and trachyte pumices are white, andesite pumices generally yellow or brown, and pumiceous basalts (for https://edenproductsltd.co.uk/2025/04/17/the-history-of-pumice-stone-from-ancient-civilisations-to-modern-day-uses/