The material cools so rapidly that atoms in the melt are not able to organize on their own into a crystalline structure. As a result, pumice can be an amorphous volcanic glass often called a "mineraloid." You can find a pumice stone at your neighborhood pharmacy, department retailer, or maybe https://edenproductsltd.co.uk/2025/04/17/the-history-of-pumice-stone-from-ancient-civilisations-to-modern-day-uses/