Gypsum

Gypsum is a very soft mineral composed of calcium sulfate dihydrate, which is thirty-six percent calcium carbonate. In 2009, the crew of the Destiny traveled to a desert planet in search of calcium carbonate to use to repair the ship's CO2 scrubbers. Near the Stargate they tested the sand and found gypsum. While the gypsum could not be used to fix the scrubbers, it gave the team an indication that the necessary components may be nearby on the planet.