The chemistry of gypsum
Pure gypsum consists of hydrated calcium sulfate: CaSO4.2H20.
These standards essentially conform with those of Victoria and New South Wales. However these eastern States of Australia do not define a Premium Grade.
We have observed that some of our competitors are inconsistent in their bag labelling. Beware of bag labelling that claims 99% gypsum and Premium Grade when the sulfur analysis does not back this up. The ratio of gypsum content to sulfur content should be 5.38 to 1 and no higher.