Exploration carried out mainly to look for possible large primary deposits of uranium ore in localities surrounding Ethiudna Hill initially addressed the potential of several hard rock showings of uranium mineralisation which had been found by previous explorers. However, these surface occurrences were quickly dismissed as lacking economic significance. In particular, 1:12,000 scale field geological mapping of a 28 square mile area downgraded the formerly recorded surface shows of uranium at Windamerta, Talbot Gum Creek and Mount Victoria, but indicated the possibility of a disseminated target existing within the many pegmatites and quartzites at Billeroo, that could be similar to the Rossing deposit in South Africa. The Ethiudna Cu-Co-Ni skarn-hosted prospect was examined to see if the mine lodes might extend outside of the two mining leases currently being held there, by looking for a continuance of structural features like those identified as influencing the known ore distribution. In addition, the possible presence of vertical mineral zoning at Ethiudna which might include uranium-bearing rocks at depth was considered. A technical review done of the results from a prior airborne radiometric survey, conducted over the subject area for a previous licensee, found that they were unreliable due to unsuitable survey parameters giving rise to poor and ambiguous data. In order to provide better regional radiometric data on which to base further evaluation of the basement uranium potential, approximately 1300 line miles of detailed new airborne spectrometer and magnetometer coverage was acquired by Esso during September 1971, but the results for the surveyed uranium, thorium and potassium channel data and interpreted anomalies are not yet available. It was decided to drill the cover sediments overlying the northern part of the licence, to test these and the unconformity with underlying basement for uranium occurrences. During November 1971, 19 open rotary holes were drilled here and each was terminated after 10 feet of cored penetration into the upper portion of the bedrock. Another 4 diamond cored holes were drilled within outcropping adamellites and migmatites just to the west of the Crocker Well uranium deposit. The total drilled footage was 3446 feet, and all holes were geophysically logged with gamma ray, SP and resistivity tools. Minor anomalous radioactivity was outlined within white clayey sands and gravels in the north-central part of the SML. A generally oxidised, in situ regolith to 260 feet thick is developed on deeply weathered bedrock. No significant sand bodies or reduced horizons conducive to the deposition of sedimentary uranium were encountered. Granitic basement cored and logged in hole 535-9 had peak gamma ray activity of 450 counts per second at 56 feet and at 69 feet depth, while the same rock yielded 375 cps in hole 535-10 at 39 feet depth. Comparable radioactivity was measured in the adamellites that were drilled in the Crocker Well area. Corresponding drill core sample assays returned no significant uranium values (maxima of 3 ppb U and 100 ppb Th in drillhole 535-9), and gave no indications of other significant metal mineralisation.