There has been a growing trend globally that new and expansions of gold projects have had to deal with much more complex ores, specifically refractory ore types. Refractory ores are regarded as those ores not amenable to standard cyanidation. A number of processes are used to enhance recovery from refractory ores i.e. Pressure oxidation, Bio leaching, roasting and ultra fine grinding.An increasing trend in dealing with refractory gold ores in Africa appears to be ultra fine grinding a float concentrate. The economic balance between fineness of the gold grain size, grinding energy input required to liberate said particles and subsequent gold recovery is paramount during the testing and economic evaluation of the project. The benefits of fine grinding a smaller volume of higher grade float concentrate material for cyanidation are examined in this paper. Producing and handling a fine grind highly sulphitic material presents some challenges. Fine grinding enables enhanced liberation of the gold particles. Specific techniques are required to take advantage of this liberation to generate better recoveries. This paper will highlight our experiences in understanding the challenges and requirements of creating and maximizing the potential of ultra fine grind gold ore.
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