Exploration undertaken by Electrolytic Zinc Co. (E-Z) looking for possible economic primary stratabound lead-zinc sulphide deposits in the ABC Range area has followed on from the earlier work of Mines Exploration done on SMLs 115, 131 and 131A, which had discovered significant but sub-economic amounts of lead-zinc mineralisation in dolomitic archaeocyathid fossil-rich rocks of the basal Lower Cambrian Wilkawillina Limestone. E-Z initially did a photointerpretative study of the target formation, to identify sites that had not previously been visited due to the rugged nature of the outcrop terrain, and then inspected the rocks to see the sedimentary facies and fossil faunal assemblages which could have influenced the setting of any mineralisation. Several minor new discoveries of willemite were made that seem to have a supergene origin and are likely to be tectonically related, being formed close to a weathered palaeosurface in the limestone and preferentially within fault breccias and joints in the rock. A new regional stream sediment survey was completed (2012 samples) which revealed many lead and zinc anomalies, the highest of which occur in the vicinity of Mount Hayward, about 5 miles north of Brachina Gorge, at the Toondana prospect. During examinations of stream sediment heavy mineral fractions from this area, willemite grains were frequently observed, suggesting good mineralisation potential. Accordingly, the area was gridded before detailed, 1:4800 scale geological mapping plus rock chip sampling for sedimentary petrological and mineragraphic determinations were performed. It was decided to diamond drill two outcropping occurrences of willemite that are associated with secondary copper (chalcopyrite-chalcocite-malachite) minerals, in the hope that richer primary sulphide ore might exist at depth in the rocks. The first drillhole, DDH T1, was completed after 150 feet of penetration into the Wilkawillina Limestone, but it failed to encounter a fault zone and cored a minimal amount of mineralisation, mostly the secondary kind formed close to thin calcite veins. At the time of licence expiry the second drillhole had not been started, but was planned to test beneath an outcrop of massive willemite located a little distance to the north-east of DDH T1.