The occurring amid aged volcanic rocks, the cavities are generally filled with deposits of secondary minerals launched by percolating water. The glass by itself forms threads, fibres, and slim partitions involving the vesicles. Rhyolite and trachyte pumices are white, andesite pumices generally yellow or brown, and pumiceous basalts (including take https://edenproductsltd.co.uk/2025/04/17/the-history-of-pumice-stone-from-ancient-civilisations-to-modern-day-uses/