Gold Pyrite, Pyrrhotite and Arsenopyrite Recovery

One of the more common classes of ores containing gold is when gold is associated with pyrite, pyrrhotite, and arsenopyrite. This is the area of gold recovery that has probably received the most research and plant optimization support especially in light of the long history of South African industrial practice. From a reagent viewpoint, charged … Read more

Dense Sludge Process

Figure 1 presents a simplified process flow diagram of the Dense Sludge process. The most significant change between Dense Sludge technology and conventional metals treatment is the method by which the alkali source is added. In conventional treatment systems, the alkali is added directly into the influent to achieve a desired pH setpoint. Generally, that … Read more

On-Stream Analysers Benefits

What are the benefits of having an OSA on-stream analyser? The assays are utilized for control in many ways, starting from individual control loops to overall optimization in the flotation circuits. Reagent dosages in the cleaner flotation stages are controlled by feedback from concentrate quality. For instance, the depressant in the zinc cleaner circuit is … Read more

Carbonaceous Gold Ore Treatment Method

Flotation The simplest method of treating a carbonaceous ore is the method described by R. W. Nice (1971) at the McIntyre Porcupine Mine where the carbon, which contains very little gold, is floated off and discarded. The remaining ore is then responsive to cyanidation. This does not work at Carlin because the carbonaceous compounds have … Read more

Thiourea Silver Leaching

Unlike base metals which are readily soluble in mineral acids, noble metals like gold and silver require the presence of oxidizing and complexing agents for dissolution. Silver approaches base metal behavior in acidic thiourea solutions (Ag + 3Thio ↔ Ag(Thio)3+ + e, E° = 0.025 V) requiring only mild oxidizing conditions for dissolution. Accordingly, the following … Read more

Hydrostatic Bearing Type Center Mechanism

Development of the Hydrostatic Bearing Mechanism evolved from the caisson thickener design. Conventional thickener mechanisms are driven by gearing which rides on ball or roller type anti-friction bearings. It would not be feasible to use this method of support with a very large diameter bearing, especially with high torque, vertical and unbalanced loads. Additional stresses … Read more

Marked Ball Wear Test

Marked ball wear testing described in a 1948 paper by Norman is an invaluable test method to measure relative and/or absolute wear rates of balls under identical mill operating conditions. Preparation of balls at Armco consists of drilling a 6.4 mm diameter hole in each ball with an electrical discharge machine (EDM), cleaning, weighing, placing … Read more

Flameless AAS Atomic Absorption Spectroscopy

Flameless AAS provides a means to increase flame AAS sensitivity, by up to 200 times. Interferences from aqueous leachates and digestates are so great, however, that flameless AAS has found application mainly after organic extraction. Thereby, the analytical sensitivity is increased far beyond that of the SX/flame- AAS methods. Interferences Interferences from other elements have … Read more

Neutron Activation Analysis for Silver

Gold values in the surveyed sulfide-poor rock units proved to be generally even lower than those in sulfidic sandstone. As a further check on this survey of mineralization, silver values began to be measured by NAA on the silver-gold beads. Radioactivity induced in silver by neutron bombardment is long-lived. The half-life of 110mAg is 253 … Read more

Falcon Enhanced Gravity Separator

Enhanced gravity separation devices (centrifuges) have been patented for over a century but were impractical until recently. The physical laws behind the concept were well understood but engineering had to catch up with the science. This included the development of abrasion resistant materials, the improved design of rotating equipment that allowed higher RPM, and a … Read more