Preliminary investigation of treatment of Coronation Hill gold- platinum- palladium ore

Abstract

Three ore types from Coronation Hill (quartz feldspar porphyry, assaying 8.6g/t Au, 0.77g/t Pt, and 1.4g/ Pd; green tuffaceous siltstone, assaying 10.4g/ Au, 1.5g/ Pt, and 4.95g/ Pd; and diorite, assaying 11.7g/t Au, 0.53g/t Pt, and 1.9g/t Pd) were studied. Gold was present as coarse and fine native gold, while Pt and Pd were present in a variety of fine grained materials. After grinding each ore type to 80% -74micron, 31%, 59%, and 36% respectively of gold was recovered by direct amalgamation. Appreciably less gold was recovered by amalgamation of a gravity concentrate. Cyanidation of either tailing extracted most of the remaining gold, leaving a residue of about 0.35g/t Au. Overall gold recovery was about 96% on all samples, with NaCN consumption of about 0.1kg/t, and CaO consumption of 1.3kg/t. No Pt or Pd concentration was produced in the gravity concentrates. Pd extractions by cyanidation were 38%, 16% and 27% respectively, but Pt levels only reached up to 7%, but the solution assays were near the detection limit of the analysis method. Flotation of gravity tails recovered 50%- 70% of the gold in the flotation feed, but tailings assays were still 1- 3.5g/t Au, so losses in flotation tails were 42%, 14%, and 33% respectively. There remains scope to considerably improve gold recoveries using flotation. However, the method produced poor results on Pt and Pd. Based on the results to date, it seems that the preferred route for gold and palladium recovery would be gravity concentration plus amalgamation of the concentrate followed by cyanidation of the combined amalgamation and gravity tails. There is as yet no satisfactory method for Pt recovery.