Difference Between Gypsum and Plaster of Paris | Compare ...
Nov 08, 2011· The key difference between gypsum and plaster of Paris is that the Gypsum contains calcium sulfate dihydrate whereas the plaster of Paris contains calcium sulfate hemihydrates.. Gypsum is a naturally occurring of Paris and gypsum both contain calcium sulfate''s hydrate form, but their water content in a molecule differs from each other.