One reason for the high value of gold is its resistance to attack by most chemicals. One exception is cyanide, specifically sodium cyanide solution, which can dissolve valuable metals. Cyanide is used to extract gold and silver from their ores, especially ores containing lower percentages of metal or those that cannot be processed using physical methods like crushing. One reason gold is highly valued is its chemical resistance, but cyanide is an exception. When sodium cyanide dissolves in water, it becomes acidic and, due to its high corrosive capability, can separate gold from rock, meaning the gold in the ore reacts with cyanide ions. Cyanide is used in gold (and silver) extraction from ores, as will be discussed below.

The use of water-based solutions for the extraction and recovery of metals such as gold is called "hydrometallurgy." Highly diluted cyanide solutions are used to extract gold. Sodium cyanide dissolves in water and gives it acidic properties, allowing gold to dissolve in the solution. The solution containing gold is called a pregnant solution, and by adding metallic carbon or activated carbon, gold can be recovered. Gold recovery from cyanide solution is an old, low-cost, and economical method. If gold is recovered via cyanidation, copper, nickel, and brass can also be conserved, yielding significant profits.

Important considerations in underground mining include high temperatures, rock fracturing, and issues with mechanized equipment. Open-pit mining uses modern and mechanized methods. In terms of capacity, open-pit gold mines are relatively smaller than underground mines and require smaller mechanical equipment. The cost of extracting one ton of ore in open-pit mines is usually less than half of underground mining, and in some cases, it can be reduced to one-tenth. Notable examples of such mines are the Cortez and Carlin deposits in the USA, which have been mined since the 1960s.

Gold recovery from gold-bearing ores extracted from mines worldwide is primarily carried out using the cyanidation process. Cyanidation is a chemical process for recovering gold and other metals dispersed in the ore in very fine particles. It is also used to recover gold mixed with sulfides. The ore or tailings are added to a cyanide solution, which produces oxygen to form a soluble compound Na[Au(CN)2]. The amount of sodium cyanide used in this process ranges from 1 to 2.5 kg per ton of ore. Cyanide reacts easily with gold, making it suitable for selective gold extraction from its ore. The diagram above illustrates a simplified overview of gold recovery from ore using cyanidation.

Human Pouyan Mining & Mineral Trading Company as the exclusive representative of Chemstar China is ready to supply all products in the processing, drilling, and extraction sector to Iranian miners and industrial owners. The company is also prepared to provide various customized equipment for domestic consumers.