The occurring between outdated volcanic rocks, the cavities are often stuffed with deposits of secondary minerals launched by percolating drinking water. The glass by itself kinds threads, fibres, and slender partitions between the vesicles. Rhyolite and trachyte pumices are white, andesite pumices often yellow or brown, and pumiceous basalts (which https://edenproductsltd.co.uk/2025/04/17/the-history-of-pumice-stone-from-ancient-civilisations-to-modern-day-uses/