The word can be used synonymously with "volcanic ash." It is actually mined from volcanic ash deposits, or it can be produced by crushing rock pumice. Inverse pityriasis rosea usually triggers a rash to the armpits or groin. It truly is an atypical form of pityriasis rosea. Learn more here. https://edenproductsltd.co.uk/2025/04/17/the-history-of-pumice-stone-from-ancient-civilisations-to-modern-day-uses/