How gold is mined

As soon as it has been decided to explore a site for potential mining activities, a range of technical actions commence, which take into account various regulations, requirements and standards. If sufficiently high grades and amounts of gold are found in a deposit for it to be considered economically viable, mining activities can be permitted and then developed. Ore can be mined from both open pits and underground mine sites. Four steps will be necessary to mine the ore: drilling, blasting, loading and hauling. Today’s operations are highly mechanized and automated and are based on large, efficient, low-energy and reliable machine and transport systems. Generally, the first processing steps are crushing and grinding. Subsequent steps are depending on the nature of the ore. In many cases, the gold is associated to a copper mineral, which means the recovery takes place simultaneously with the recovery of copper, and the production of pure gold takes place at the smelter. In many cases, gold can be recovered using gravity processes such as shaking tables. In the global perspective, however, most gold is recovered using cyanidation. Such processes have been used for more than one hundred years to improve the processing results and to eliminate the need for mercury amalgamation. Cyanide is a substance, which has the ability to extract gold and silver from ore at very low concentrations. The leaching process involves formation of complexes of gold and cyanide, and the use of activated carbon to bind the gold complexes. From the carbon then, the complexes can be extracted and the metal can be recovered e.g. by application of a subsequent electrowinning process. Refractory gold – gold in a form not directly amenable for cyanidation - may require oxidation, e.g., bio oxidation, in order to liberate the gold and make it accessible to cyanidation. 

After finishing mining, the exhausted mine site will be rehabilitated and given back to nature for further uses such as a wildlife habitat, recreation or building. This practice is the standard used in Europe today. According to a reclamation plan put in place and depending on the properties of the mining waste, the waste deposits are decommissioned either by covering with soil or equal material, or by inundation using water. The key parameter is then to avoid exposure of the pyrite content to air. After covering, vegetation is established, or measures to secure the water cover are put in place. The area is then adapted to the most appropriate post mining land use, which may vary from case to case.