gypsum

As nouns the difference between gypsum and gypwater

is that gypsum is a mineral consisting of the hydrated calcium sulphate when calcined, it forms plaster of paris while gypwater is water with a high level of dissolved gypsum which can cause diarrhea [http://wwwranchesorg/desperadoshtm].

As nouns the difference between gypsum and coralloid

is that gypsum is a mineral consisting of the hydrated calcium sulphate when calcined, it forms plaster of paris while coralloid is a small node of calcite, aragonite or gypsum that forms on surfaces in caves, especially limestone caves.

As an adjective coralloid is

having the shape or form of coral.