Radium Hill developed from the discovery in 1906 of an outcrop of davidite, a complex oxide composed of rare earths, uranium, iron and titanium. The deposit was worked on a small scale up to World War 1 as a source of radium. In 1944, the Federal Government received a request from Britain for assistance in evaluating Australian uranium provinces. World War 2 ended before the programme was completed, and the SA Government took over the project in this State. By 1951, the Government was in a position to negotiate a seven year contract with the Combined Development Agency of the United States and United Kingdom for supplying it with locally refined uranium oxide that was produced from Radium Hill ore. Development of the deposit presented many technical and organization problems, and new processes for concentration of ore and extraction of uranium had to be developed. The Department of Mines’ Research and Development Branch, later to become Amdel (the Australian Mineral Development Laboratories) Ltd, was formed for this purpose. In terms of its geological setting, Radium Hill is a locus of greatly increased igneous activity, with amphibolitised gabbros of two ages, aplitic microgranites and rare earth pegmatites being restricted to the immediate vicinity. There were several distinct periods of formation of mineralisation, with uranium introduction being last. The uranium mineralisation post-dates the plug amphibolites but pre-dates the microgranites and probably the dyke amphibolites. The source of the uranium is unknown, but the soda microgranites are a potential source. The amphibolites seem to offer host conditions in that uranium values are often concentrated in their immediate vicinity. Uraniferous lodes at Radium Hill occur as shear replacements and infillings along medium-high angled reversed fault or overthrust type fractures developed within a domed anticline (northeast-southwest major axis) in granitised meta-sediments. At least three major parallel fault shear zones have developed lodes along part of their length over a zone some 3000 feet long, and there are others relatively unmineralised. A typical association of normal and transcurrent faults displace the lodes at intervals and the latter also cause lode splitting and inhibit ore formation locally. The original shape of the overthrust shear planes, which exhibit central flattening, possibly in part related to doming influence, have apparently resulted in a curvey form of each of the ore bodies being displaced horizontally relatively to the north-east. The lode lenses, therefore, have north pitch in the north and a south pitch is anticipated in the south. Greatest lode widths appear to accompany broader changes in lode strike.