MICROBIAL PRETREATMENT OF REFRACTORY SULFIDE AND CARBONACEOUS ORES IMPROVES THE ECONOMICS OF GOLD RECOVERY.

An objective of this study was to evaluate the use of acidophilic, thermophilic microorganisms for pretreating refractory gold ores. In addition, carbonaceous gold ores were tested with the thermophiles to determine whether bioleaching alone would be sufficient to achieve acceptable gold recoveries. Test ore samples consisting of ores, concentrates, and tailings were received from various locations within and outside the US. Most of the carbonaceous gold ore samples were obtained from the Southwest. Combining bioleaching with either carbon-in-leach cyanidation or blanking agent pretreatment is required to achieve satisfactory gold recoveries from these ores.