The gypsum deposit is a dune formation situated on the south eastern margin of Lake Fowler, 9 miles west of the out port at Edithburgh, on the east coast of Lower Yorke Peninsula. The gypsum occurs in two forms - mainly "seed" with interbedded and a superficial layer of "flour" - and the marketed product consists of an admixture of these varieties. The overall average sample from the main deposit contains 92.9% Ca3O42H2O. The chief impurity is a finely divided clay derived from underlying glacial deposits. Gypsum production from 1905 to the end of 1949 was 315,000 tons. The reserves remaining are estimated to be of the order of 1,430,000 tons, of which 980,000 tons constitute one very prominent ridge - "main gypsum dune" - held under Miscellaneous Lease by the South Australian Gypsum Company. This company is the chief producer from the deposit. The main output is exported to New Zealand for use in cement manufacture and as a fertilizer. A small proportion is used for plaster manufacture. Present production amounts to about 10,000 tons per year and could be expanded considerably. The gypsum is easily won by mechanical open cut mining. The deposits lie within a short distance of Edithburgh where facilities exist for loading on to coastal and overseas vessels.