Golden Reef Mining employs heap leaching technology to process its oxides.Gold heap leaching is a hydrometallurgical process designed to treat amenable low-grade gold ores that contain roughly 0.5 gram per tonne (g/t) gold to 1.5 g/t gold. The ore is stacked to a height of 4 metres by various types of equipment on an impermeable highdensity poly ethylene (HDPE) membrane, and a water-based solution, or leachate Â containing 0.03%- 0.06% sodium cyanide (NaCN) is applied to the surface of the stacked ore. Gold, silver, and other materials contained in the ore are dissolved to various degrees by the leachate as it percolates downward through the stack of ore and are collected at the bottom of the heap. The cyanoaurite ion is produced when gold is exposed to the cyanide solution. The pregnant solution, or metal-bearing leachate that contains the precious metals gravitates to the pregnant pond where it is directed to the carbon columns where the metals are extracted, and barren solution is then reapplied to the top of the stack.
As Golden Reef Mining we are irrigating our leach pads for two months before putting them off leach in order to add another lift or releach them and we are getting an average recovery of more than 75% and is consistent with the results from the amenability tests done on the ore.
Golden Reef Mining uses Carbon in Column (CIC) to extract gold from the pregnant leach solution (PLS). The PLS is pumped through a set of six carrousels containing 400kg of activated granular carbon. The gold, silver and some metals are preferentially adsorbed on the activated carbon. Our adsorption efficiency is more than 95% and we consistently do acid washing to remove inorganic foulants from the carbon. The gold is then stripped from the carbon in a PG boiler using a hot solution (120Â®Celcius) of 5% Sodium Hydroxide with 2% Sodium cyanide. On average 90% of the gold is eluted and electroplated the wirewool which is removed and acid digested at the end of the elution process. The gold concentrate from digestion is the calcined and smelted to produce gold bullion.