As part of continuing exploration for possible economic buried stratiform / hydrothermal copper mineralisation in the Yudnamutana Mining Field, the target lower Callanna Group strata were geologically mapped, petrologically studied and geochemically sampled at surface, and scout rotary percussion drilling of the Wywyana Formation (22 holes for a total penetration of 10,490 feet) was undertaken during April-May 1973. 1:240 scale detailed mapping was carried out over the area of the Pinnacles West grid, and 241 rock outcrop samples were collected for petrological examination. Another 128 rock chip samples were taken to assay for copper. Also within this area, two costeans totalling 275 feet in length were bulldozed and trench sampled (48 samples), again for copper. 14 of the drillholes encountered significant (>0.25% Cu) mineralised intercepts at varying depths within a biotite-actinolite-hornblende marble unit, this mineralisation comprising mainly disseminated fine grained chalcopyrite plus pyrite, magnetite and lesser chalcocite and malachite. The best, narrow but rich intercepts came from the Wheal Austin prospect in the south-west of the licence, where hole YX23 encountered 2.61% Cu from the depth interval 285-315 feet, while hole YX24 returned 1.39% Cu from 95-145 feet depth, including 7.2% Cu from 115-120 feet. At the Pinnacles prospect, adjacent holes YX14 and YX16 both returned 1.6% Cu from the depth interval 70-105 feet.