The Paulsens gold deposit in the Pilbara region of Western Australia was discovered by CRA in 1998. In 2001, St Barbara Mines Limited (St Barbara) made a successful takeover offer for Taipan Resources NL and then began an update of the previous Bankable Feasibility Study (BFS) undertaken by Minproc Limited. This paper describes the history of the metallurgical testwork, plant design and initial development to optimise a project with complex metallurgical process characteristics and manage the risks. The Paulsens ore is preg robbing, has cyanide soluble copper and nickel and is highly sulphidic. The ore is relatively hard and requires a very fine grind size of P80 53 microns. The metallurgical challenges have been met for this complex ore and the process flowsheet included aspects not commonly associated with a typical gold plant. Geometallurgicai mapping of the global ore body to understand the variability of cyanide soluble copper and nickel as well as potential problems from preg robbing waste was undertaken to assess the risks and suitability of the proposed flowsheet. Concurrently, the mine schedule could be optimised to manage the levels of copper and nickel in the feed by understanding the copper behaviour with respect to block modeling. Problems encountered, which will be discussed and project examples noted, with cyanide soluble gold in Carbon in Pulp (CIP) plants include: High cyanide consumption; High WAD (weak acid dissociable) stabilised in tailings dams and high tailings return water levels; Determining the free cyanide level in the leach solution; Preg robbing of gold onto copper minerals; Very high copper loadings on the carbon resulting in high gold solution losses to tails, poor carbon activity, Dore gold bars with low fineness and increased refining charges; Very high oxygen demand limiting gold leaching kinetics; and Increased ferrocyanide and ferricyanide levels in solution impacting on the leach and adsorption.
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