The Colonial Sugar Refining Company Limited submitted samples of dune gypsum material from Lake Fowler for treatment; A product free from fine, or flour, gypsum was required. Air separation methods had been used on dried material from this deposit in previous work but work on gypsum samples from other deposits had shown that wet-attritioning at high pulp density was necessary to effect a good separation of the adherent flour from seed gypsum. However double drying of the raw feed, once for direct dry separation and again after wet attritioning, is costly and it was decided to investigate complete treatment by wet methods.In this report the terms "seed" and "flour" will be used to describe the granular and powdery types of gypsum respectively.