1. Calcium sulfate hemihydrate in statoliths of deep-sea medusae
2. The worldwide stocks of natural gypsum are estimated to be several trillion (1012 t) tons. The annual delivery rate of natural deposits is about 100 million tons (Mtpa) of gypsum and anhydrate. Furthermore, 150 Mtpa are generated from the synthesis of phosphoric acid, 45 Mtpa from the flue gas desulforization process, and more than 25 Mtpa from other industrial processes. The worldwide production of cement is even higher, with an annual output of about 2500 Mtpa, but cement is a mixture of different materials, and has a content of 1-5 wt % of calcined gypsum. Numbers are taken from The Economics of Gypsum & Anhydrite, Roskill Information Services, 9th ed., 2004.