A government investigation of the economic potential of the abandoned historic Burra Burra copper mine was started in December 1961. The SA Department of Mines (SADM) initial work comprised 1:1200 scale geological mapping of the old mine area, followed by 1:240 scale mapping and surveying of the 1860s era open cut excavation (dimensions 1200 feet long x 350 feet wide, on average, x 120 feet deep (an estimated maximum depth, due to it now being a partially water-filled pit)). The recorded old underground workings beneath the open cut extend over a length of 3543 feet, with the deepest level at 85 fathoms (510 feet), while the deepest shaft (Morphetts pumping shaft) reaches 100 fathoms (610 feet) below the surface. A programme of dry rotary drilling of near-horizontal holes into the western and south-western walls of the historic open cut was carried out by the SADM between 17/1/1963 and 6/11/1964, with 12 holes completed for a total penetration of 2803 feet. As well, two deep, inclined and wholly cored diamond drillholes were put down on the southern rim of the open cut to test for possible sulphide mineralisation beneath the old underground workings. However, both of these latter holes were abandoned before attaining their 1500 feet target depths because of hole caving due to the broken nature of the ground. Burra DDH1 reached a TD of 766 feet 9 inches, but its core recovery was only 58.7%. Burra DDH2 was located 1000 feet south of Burra DDH1, to probe below the workings extending from Morphetts Shaft. It reached a TD of 849 feet. Traces of copper sulphides were recovered from the heavy mineral separates of crushed drill core samples taken over the depth interval 815-830 feet in Burra DDH2. The core recovery in this hole was 81.1%. The overall grades and dimensions of the sulphide lodes found by the old underground miners in carbonate rocks below the mine 50 fathom (300 foot) subsurface level are not known. However, early eyewitnesses' estimates indicate that the grade may be about 3% Cu. A follow-up programme of appraisal percussion drilling centred on the old open cut was next undertaken by SADM between October 1964 and April 1965, when 16 vertical holes were drilled for a total penetration of 2055 feet, with the intent of better evaluating the grade and reserves of the remaining secondary copper ore. Selective open tube coring was done to obtain samples for logging and assay. Six of the drillholes were sited in the floor of the open cut, while the other ten were sited on mine benches further south. Preliminary drill-based evaluation of the remnant oxidised ore resource, taken to a depth of 98 feet 5 inches below the water level in the open cut, has indicated that ore reserves exceeding 1 million tons are present, with an average grade of 1.44% Cu. Substantial further reserves of similar oxidised ore have also been indicated by costeaning and drilling carried out in the area to the north of the open cut. In addition, more than 200,000 tons of broken 'attle' rock with an average grade of 1.2% Cu have been outlined in the mine dumps. Because of the non-carbonate nature of the ore host, the mineralised rock is amenable to low-cost acid leach beneficiation, with processing trials conducted to date giving very good copper recoveries. Possible evidence of an igneous origin for the Burra ore was found early in 1965, based upon the petrographic/mineragraphic identification of a potash-felspar porphyry carrying pyrite, chalcopyrite and bornite, which is exposed as a small plug near the centre of the open cut, on the western side of the water table pool (cf. Geological Survey of South Australia, Quarterly Geological Notes, vol. 17, pgs 1-5).