RG Gold is currently producing c. 33Koz of Gold in Dore from heaps, with our expansion program expected to increase production by 50% in 2018. We are committed to the latest heap leaching technologies to increase efficiency and drive down costs
Physical and Chemical Composition of ore
Samples of primary ore from the the South and the North Raygorodok are very similar in terms of their component composition. Gold is the only commercially valuable component, other metals have grades of 1/100 of a percentage point. In addition, harmful impurities such as arsenic and antimony are less than 0.03% across almost all samples.
Main ore minerals in the primary samples are represented by free gold, pyrite and magnetite. Rock-forming minerals are quartz, amphibole, albite, chlorite and others in smaller amounts. Gold is mainly in a free form and in coarse intergrowths with pyrite, galena and quartz, or in microfissures of pyrite and quartz.
Elution and Carbon Reactivation Process
During the process, an alkaline cyanide solution is used to leach gold from the ore. The gold ions are then concentrated and separated from the slurry by a process of adsorbing onto activated carbon. The next stage of the process is elution, where the adsorption of the gold onto carbon is reversed (desorption).
To accomplish this, the loaded carbon is removed from the processing circuit where the gold is stripped in a multistage process, resulting in a ‘pregnant eluate’ soltion with a high gold concentration. The gold is then separated from the eluate by electrowinning (electrolysis) onto steel wool cathodes.
In addition to stripping the gold from the carbon, the elution process also incorporates an acid wash to remove any inorganic foulants from the carbon which reduce its activity. Any organic foulants such as oil must be removed in a separate process of thermal reactivation. This involves heating the carbon in a gas fired reactivation kiln to vaporise the remaining foulants. The reactivated carbon is then returned to the circuit, where the adsorption, desorption and reactivation cycle begins again.
Roasting and Melting
Following electrolysis, the gold bearing steel wool is removed from the cathodes and delivered to the oven to separate non-ferrous metals and iron from the gold. Roasting takes place at a temperature of 650C, where air is introduced to oxidise the environment and reduce the roasting time to between 5 – 10 hours.
Nitric and hydrochloric acids are used for processing, and once the dissolved gold has settled, the system is drained and the cathodic remains are placed in the melting furance at a temperature of 350C to dry. Once dried, temperatures of up to 1060C melt the material at which point the bullion is poured into a slag pot. An ingot is released once the bullion has cooled down.
Ingots are cleaned and smoothed before sample drilling to determine gold and silver content before stamping and shipping for affinage.
Our quality control department (QCD) provides systematic inspection at each stage of the process to ensure rigorous standards are met.
Ore delivered to the ragging and agglomeration stages is measured and recorded using conveyor scales. Ore sampling of the heap leaching metal can determine the defined gold, humidity, volume weight and granules percolation using electromagnetic and ultrasonic flowmeters.
The control of cyanide concentrations throughout the process is performed by a standard titration method, and the pH of these solutions is measured and controlled using portable pH-meters.
Control of the gold content in the product, process solutions and sorption columns is performed by a sample drip selection for each shift. The volume of metal in the sorption columns, and the staturation and delivery of the eluate back to the sorption columns, is measured by the carbon layer height in the tank.
Control of laboratory operations is performed via encoded samples for internal and external control.