South-westwards inclined diamond drillhole No. 11 was put in to 400 feet total hole depth by licensee Kennecott during the subject reporting period, to investigate the postulated buried inland extension of a continuously mineralised sheet-like body of of felsic igneous rock drilled in the company's earlier-completed holes 1, 4 and 10 sited on the south-eastern corner of Spilsby Island. However, no indications of economic thicknesses or grades of open cut mineable subsurface ore were seen in DDH 11 (the economic cutoff grade for this being taken as 0.1% MoS2). Detailed petrographic studies of drill core samples could not discern any correlation between rock type, metasomatic alteration mineralogy and the occurrence of the sought-after sulphide mineralisation. In consequence of these findings, Kennecott decided to abandon exploration of the prospect. Although the new hole disproved the shallow orebody model, but it also revealed a deeper intercept, over the narrow depth interval 150-160 feet, of an odd skarn-type mineralised rock which bears molybdenum, tungsten, copper and bismuth having an average metals' content combined grade equivalent to 0.2% MoS2. [After 21/8/1967, the island was subsequently reserved for a second time from public exploration, to allow the SA Government to continue to drill there with its own equipment which had been contracted to Kennecott in July 1965 and placed onsite (whereby another four diamond holes were drilled; see RB 66/61 for a description of these later drilling results)].