Hydrated Calcium sulfate, or gypsum, is a chemical compound with the general formula of CaSO4 + H2O was found on Mars in 2011 by the Opportunity rover. A surface vein was identified on the Martian surface.
The main use of Calcium sulfate, when adequately treated with heat (dehydrated), is plaster of Paris, or stucco. This is used as a finishing compound, or as an element of drywall construction. Drywall construction can provide fire safety for structural elements.