Cyanide-free gold processing refers to alternative hydrometallurgical technologies and reagent systems used to leach and recover gold from ores and concentrates without the use of sodium cyanide (NaCN), which is the conventional and most widely used gold lixiviant globally. The development and adoption of cyanide-free processes is driven by the significant environmental and regulatory concerns associated with cyanide toxicity, including the risk of cyanide spills, tailings facility failures, and impacts on aquatic ecosystems and human health. Established alternative lixiviants include thiosulfate (used commercially by Barrick Gold at the Goldstrike operation), thiourea, halide systems (chlorine/bromine), and glycine. Newer commercial technologies include the CSIRO-developed glycine leach process and various proprietary systems such as Clean Mining's glycine-based approach. Cyanide-free processes are particularly relevant for mining operations in jurisdictions that have banned cyanide use, such as the Czech Republic, Hungary, and some regions of South America, as well as for operations seeking social licence to operate in environmentally sensitive areas. While cyanide-free processes can achieve comparable gold recoveries to cyanide in some ore types, they often involve higher reagent costs, slower leach kinetics, or more complex solution chemistry, requiring careful economic and technical evaluation.
