The Stenhouse Bay Gypsum deposits are the chief source of gypsum for the Australian and New Zealand plaster industries. They have been worked for over 60 years and the total recorded output to 31st December, 1949, amounts to 1,986,422 tons. Present production if of the order of 150,000 to 200,000 tons per annum of which 95% is exported to the eastern states and New Zealand. The marketed product is extremely pure and contains 95-96% gypsum. it is mined at very low cost by simple quarrying methods from shallow lake deposits, washed, and loaded by conveyor belts into ships. Production is limited by the availability of shipping and falls far short of actual demand. The gypsum occurs in two forms - "flour" and "rock", but to date only the rock gypsum has been worked. The known reserves of rock gypsum of 95-96% grade are estimated at 2½ million tons, equal to the quantity already extracted, and sufficient for 10 years at the present rate of production. The reserves of flour gypsum of 80-85% grade and higher, so far unexploited, are estimated at 3 to 4 million tons in Marion Lake, the scene of current operations, and an additional 6 to 8 million tons are likely to be proved by boring in Snow's Lake. The chief impurity present in the flour gypsum is amorphous calcium carbonate which can be removed by a simple washing process to yield a product equal, if not superior, to that at present being obtained from the rock gypsum. In view of the limited reserves of rock gypsum the future of the industry depends on the successful bulk handling and use of the large reserves of flour gypsum. The handling and treatment side of this problem are discussed in the reports of A.T. Armstrong, State Mining Engineer and of N. Jackson, Metallurgical Engineer. Geologically, the deposits are similar in composition and origin to those at Lake MacDonnell but are not nearly as extensive. If possible they should be conserved for a local major manufacturing industry and the Lake MacDonnell deposits exploited chiefly for export market of crude gypsum. The Stenhouse Bay deposits are located close to the seaboard with ready access to Adelaide by sea transport. Their logical development would be for the production of manufactured gypsum products in South Australia for local consumption and for export interstate and overseas. It is obvious that manufactured products have a considerably higher value and can afford to be transported over greater distances than the raw gypsum and in consequence would commend much larger and wider markets. The gypsum resources of the State may be ranked next in importance to iron and there is no reason why this industry should not be developed during the next ten years to supply the major requirements of the rapidly expanding building industry in Australia. Such a development would eliminate the costly exploitation of a large number of deposits unfavourably situated, mostly small, and many consisting of low-grade material. This might best be accomplished by the establishment of a modern plant adjacent to Adelaide for the manufacture of a wide range of gypsum products.