The developing between old volcanic rocks, the cavities are frequently crammed with deposits of secondary minerals released by percolating h2o. The glass itself kinds threads, fibres, and thin partitions between the vesicles. Rhyolite and trachyte pumices are white, andesite pumices usually yellow or brown, and pumiceous basalts (such as take https://edenproductsltd.co.uk/2025/04/17/the-history-of-pumice-stone-from-ancient-civilisations-to-modern-day-uses/