Calcium sulfate or CaSO4 is also known as gypsum. It can be used to boost sulfate or add permanent hardness to a mash. You will want to verify with your vendor, but one gram per gallon typically adds 62 ppm calcium,147 ppm sulfate, and 153.5 ppm to the permanent hardness.
Calcium carbonate or CaCO3 is precipitated chalk. It is typically used in brewing as a water adjustment to increases the pH of a mash. You will want to verify with your vendor, but 1 gram per gallon usually adds 106 ppm calcium and 158 ppm carbonate.
Calcium Carbonate \ Chalk