In early 1983, mineral prospector Peter Tayler discovered a near-surface secondary occurrence of magnesium and sodium sulphates in a creek-bank exposure of Mesozoic shales, deposited at the base of the Lower Cretaceous Bulldog Shale near the western margin of the Eromanga Basin, 17 km north-east of Coober Pedy. The fine-grained, acicular clear to whitish evaporite minerals epsomite and bloedite were seen to be disseminated in these beds, and are also present concentrated in bunches at the top of a waxy lacustrine shale horizon. Subsequent geological mapping and reconnaissance rock chip sampling of this host unit has confirmed the widespread occurrence of these soluble sulphate salts in this part of the Stuart Range 'Breakaway' country, always associated with limestone, glauconite and gypsum - bearing shallow marine and lacustrine shaley facies, for the most part concealed beneath a thin veneer of residual overburden. The highest grade and greatest thickness of the sulphate mineralisation seems to have developed under the following optimum conditions: forming within dark grey waxy shales having bentonitic characteristics, on north-facing exposures of river embankments, in places where transported overburden is absent. Accordingly, it appears certain that these salts accumulate near the surface as a direct result of the capillary action of saline groundwater, and that a cover of transported overburden tends to inhibit that action. Rock assay data show that the grade of soluble sulphate mineralisation varies widely, but, in general, the better grades (up to 20.5% MgSO4 by weight) are found in the south-western part of the 469 square km subject exploration licence area taken out over the find. Diminution of grade is apparently due to the presence of a more silty to sandy sedimentary facies in the host lower member of the Bulldog Shale. The assay data also reveal that the sodium and magnesium salts exist in roughly similar percentages in situ (or in a ratio of 35:65 as anhydrous mineral equivalents). Following the farm-in of CRA Exploration to the licence in mid-1984, a systematic programme of backhoe costeaning and trench wall sediment logging and sampling was undertaken over the EL area at 183 sites, and economic studies of the viability of artificially producing potassium sulphate from the magnesium sulphate were instigated. A total of about 7 Mt of MgSO4 was outlined in three separate areas at an average grade of roughly 7.4%, using a 5 m% cut-off grade. Samples of the host shales gave an oil yield of less than 5 l/t through Fischer distillation. Bench scale testwork of mineral extractive techniques carried out by CRA Research in Newcastle, NSW was unable to separate out the salts by leaching, due to the fine nature of the parent clays. Indicated low salt recovery, poor solid/liquid separation and high moisture content of the leach residue made the envisaged production flowsheet unworkable. The technical problems proved insurmountable, so CRA Exploration chose to terminate the farm-in agreement with the licence holder in November 1986. No further testwork was conducted during the following ten months. Eventually it was decided to allow tenure to lapse.