As soon as the SA Government restored public access to the subject ground within Spencer Gulf that it had temporarily reserved from the provisions of the State's Mining Act, Kennecott Explorations (Kennecott) took up SML 85 there to evaluate an occurrence of vein molybdenite and scheelite which had been discovered on Spilsby Island in 1946 and later confirmed in 1963 by geologists of the South Australian Department of Mines, while they were prospecting for tungsten mineralisation. The occurrence lies on the extreme south-eastern end of the island, as a vein network exposed over an area of 400 feet x 300 feet within granite outcropping on the wave-cut shore platform; it presumably extends both landward beneath the island's Recent kunkar cover and in the opposite direction beneath the sea. To evaluate the occurrence, Kennecott undertook two campaigns of diamond drilling on the island, the first during September-November 1965 (10 vertical holes for a total penetration of 647 feet 4 inches), and the second during January-March 1966 (when existing DDH4 was deepened by 50 feet 7 inches, and an extra, 55 degrees inclined hole, DDH10, was drilled to TD 401 feet 8 inches). Eight of these drillholes encountered visible molybdenite, but only three of them (DDH 1, 4 and 10) intersected a body of possibly ore grade mineralisation. Preliminary estimated reserves, based on the drillhole data, are 0.5 million tons @ 0.46% MoS2 (+ 0.145% WO3), at a cut-off grade of 0.14% MoS2, assuming an average orebody thickness of 25 feet, width of 500 feet and length of 500 feet. During December 1965, Kennecott geologists made a reconnaissance of the other nearby islands to check some SADM-reported molybdenum and tungsten geochemical anomalies, but no other mineralisation was seen. On Spilsby Island, detailed 1:480 scale geological mapping of the mineralised zone revealed that the granite host varies in character, with three main rock textural types being present, but most of the mineralisation appears to have formed in just one type, an even-grained quartz-microcline(-plagioclase-biotite) granite. All three granite types occur in well defined, low to moderately dipping 'bands' which have regular boundaries. The bands vary in width from a few inches to tens of feet. Most of the exposed molybdenite and scheelite occupies thin, low angle, north-westwards dipping veins in the south-eastern part of the mineralised zone, while in its south-western part fewer but similar veins dip towards the north-east at angles of between 20 and 40 degrees, i.e. in both cases aligned sub-parallel to granite band boundaries.