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Cyanide leaching "heap" at a gold mining operation near Elko, Nevada. On top of the large mounds of ore, are sprinklers dispensing a solution of cyanide. Gold extraction is the extraction of gold from dilute ores using a combination of chemical processes. Gold mining produces about 3600 tons annually, [1] and another 300 tons is produced from ...
The dominant method for refining gold is a cyanide extraction method, or gold cyanidation, introduced in the late 1800s. This a metallurgical technique used to extract gold from lower grade ores by converting gold into a water-soluble coordination complex. [52] [53] Finely ground rock is treated with a solution of sodium cyanide.
The Newbery-Vautin chlorination process is a method for extracting gold from its ore through the use of chlorination. This process was jointly developed by James Cosmo Newbery and Claude Vautin. Background
Gold cyanidation (also known as the cyanide process or the MacArthur–Forrest process) is a hydrometallurgical technique for extracting gold from low-grade ore through conversion to a water-soluble coordination complex. It is the most commonly used leaching process for gold extraction. [1]
The Merrill–Crowe Process is a separation technique for removing gold from the solution obtained by the cyanide leaching of gold ores. It is an improvement of the MacArthur-Forrest process, where an additional vacuum is managed to remove air in the solution (invention of Crowe), and zinc dust is used instead of zinc shavings (improvement of Merrill).
This method is an acid heap leaching method like that of the copper method in that it utilises sulfuric acid instead of cyanide solution to dissolve the target minerals from crushed ore. The amount of sulfuric acid required is much higher than for copper ores, as high as 1,000 kg of acid per tonne of ore, but 500 kg is more common.
For example, 99 tons of waste is generated per ton of copper, with even higher ratios in gold mining – because only 5.3 g of gold is extracted per ton of ore, a ton of gold produces 200,000 tons of tailings. [72] (As time goes on and richer deposits are exhausted – and technology improves – this number is going down to .5 g and less.)
The economic viability of a deposit will also depend on the grade and tonnage of the reserves of a deposit, along with the costs associated with extracting the ore. Methods of delineating reserves and of extracting gold ore are improving over time, increasing the possibility for production of more gold. [47]