A peculiar occurrence of anhydrous sodium sulphate, thenardite, has recently been discovered below the salt crystallizing pans at Didwana, Jodhpur State, India. Here salt (NaCl) is crystallized out by evaporation in open pans from brine obtained by sinking wells alongside the pans, to a depth of about 15–20 feet below the surface. The land surface consists of very fine sandy silt and the salt-pans are made by cutting shallow depressions about 120 feet long by 85 feet wide, a low ridge of silt about 2 feet high and 3 feet broad being left between them. The pans are cleaned out at the beginning of the salt season (February-March): the brine from the wells is run into them to a depth of 1 to 2 inches and the salt crystallizes out by evaporation.