A detailed understanding of ore mineralogy and elemental deportment is required to select the optimal processing route for the extraction of valuable metals from ore, such as copper and gold. However, common ore characterization techniques, such as Mineral Liberation Analyser (MLA), are costly and time-consuming. Diagnostic leaching is potentially a cheaper and simpler alternative for the determination of the mineralogy and deportment of valuable minerals within an ore, involving the use of selected reagents and conditions to dissolve targeted minerals. Traditional diagnostic leaches currently used in processing plants worldwide, use sodium cyanide and sulfuric acid as reagents to provide details on copper and gold recoveries. This paper shows that these leaches can provide information on not only gold and nuisance copper recoveries for gold ores but also information on trace element recovery, mineralogical associations, reagent consumption and speciation. Leaches conducted on a gold ore sample set indicated variances in gold and copper recoveries, owing to the differing mineral concentrations and types. Low gold recoveries were attributed to the ore being refractory in nature. Chalcopyrite and pyrrhotite were found to contribute directly to the formation of thiocyanate. The importance of monitoring impurity element concentrations was demonstrated, since some sample leach liquors contained high toxic trace element concentrations. The use of additional information (reagent consumption, trace element recovery etc.) from diagnostic leach data may prove to be of great advantage in process design or optimisation.
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