Evaporite minerals in black shale at the base of the Early Cretaceous Bulldog Shale near the western margin of the Eromanga Basin were the target about 50 km NE of Coober Pedy. Reconnaissance mapping, soil sampling, auger drilling and the backhoe digging of 57 costeans defined the sporadic near-surface concurrence of bloedite (magnesium sodium sulphate) and epsomite (magnesium sulphate) salt concentrations. The best intercept obtained was 1.8 m @ 30% total soluble salts. In a search for the source of these Mg-rich evaporite minerals, rotary mud drilling of 3 vertical cased holes for 296 m during November 1983 located brines dominated by sodium chloride (85% NaCl) occurring within a Cadna-owie Formation sandstone aquifer underlying Lake Cadibarrawirracanna. This aquifer has a salinity of ~55,000 ppm and is capable of flowing at an estimated 15,000 gallons per hour (~56,800 l/s). Shortly afterwards, diamond drilling of 1 vertical hole 83LCD1 (TD 408 m) into Lower Permian shales lying beneath the Cretaceous aquifer at the margin of the Boorthanna Trough failed to locate older host sequences suitable for hosting evaporitic minerals, or to identify any evidence of volcanic activity. Consultants were commissioned in October 1984 to conduct a preliminary economic study on the economic viability of attempting magnesium sulphate production from the known occurrences. A set of 40 kg bulk mineral samples were extracted and sent to CRA's Research Div. in Newcastle, NSW for undergoing bench scale leaching tests. The main results achieved were: a) there is good agreement with Amdel's head assay values b) some very fine insoluble residues remain after leaching, 80% of them passing a 5 micron screen c) leaching on 3 mm topsize ore is complete in 2 minutes. On 14/10/1986, 940 square km of EL 1165 were partially relinquished. The remaining 363 square km of ground were chosen to allow for exploration for base and precious metal mineralisation that may possibly exist in concealed basement.