Cyanide has been used in the mining industry for well over 100 years and, with proper management, can be used safely and without harm to the environment. In modern times, there have been significant scientific advances in the use of chemical and biological reactions to convert cyanide to less-toxic chemicals.
Gold cyanidation, a process in which gold is temporarily converted into a water-soluble form, is the most widely accepted method for efficient and environmentally sound gold extraction.
Donlin Gold plans to use this practice to extract the gold from the ore, and will follow guidelines provided by the International Cyanide Management Code on how to handle cyanide from its manufacturer to its transport, storage, use, and disposal.
Dry sodium-cyanide briquettes will be shipped to the mine site in sealed steel ISO (International Standard Organization) tanks that are waterproof and can float. The cyanide will be dissolved into a weak, pH-controlled solution for use in gold extraction. After the ore is crushed into smaller-sized grains, it will be transported to an on-site leaching plant, where the ore will be mixed with cyanide. The cyanide will dissolve the gold into a solution, then the gold will be precipitated out of the solution.
The cyanide solution will go through a destruction process that reduces its concentration. This industry-leading detoxification process has been adopted in the last 25 years by major gold-mining companies worldwide. The trace amounts of cyanide remaining in the tailings-storage facility will disintegrate further under the influence of sunlight and air.