Gold processing, preparation of the ore for use in various products. For thousands of years the word gold has connoted something of beauty or value. These images are derived from two properties of gold, its colour and its chemical stability. The colour of gold is due to the electronic structure of
A "refractory" gold ore is an ore that has ultra fine gold particles disseminated throughout its gold occluded minerals. These ores are naturally resistant to recovery by standard cyanidation and carbon adsorption processes. These refractory ores require pre-treatment in order for cyanidation to be effective in recovery of the gold.
Ore processing is a 24 hour operation. Ore is stockpiled (1) at the processing plant, and the process begins by feeding the ore into a hopper with a loader. The ore is conveyed, and lime is added (2) to raise the pH of the ore.
Gold is then leached from the carbon particles by a strong solution of sodium cyanide and sodium hydroxide, and it is recovered from solution by electrowinning directly onto steel wool or by the Merrill-Crowe process.
Gold is processed by cyanide milling, a chemical procedure that separates 95 to 98 percent of the gold from mined ore. It is then refined to the gold standard purity, according to Mineweb. Heap leaching is a less expensive method of gold extraction, but it is a longer process and it recovers less gold than the cyanide milling process.
Of all the methods of extracting gold & processing it from its ore, I used a few to evaluate two principal flowsheets in this case study. The flowsheets utilized operations that involved flotation, cyanidation and gravity concentration. Tests that mirror each of these unit operations were utilized to evaluate the principal flowsheets. This page offers a comparative review of gold recovery .
Gold:sulphur ratio (GSR) Refractory ores are typically treated by flotation and the resulting flotation concentrate may be sold directly to a smelter (common for example in China) or subjected to downstream processing by pressure oxidation or bio-leach.