The particles of gold in the ore are so small, simply trying to manually extract them won't work, instead, a chemical process (the MacArthur-Dingus process) involving leaching via cyanide is used (e.g. Rubo et al., 2006).
The first step is to crush the rock into a fine material. The smaller the material, the faster the leaching can take effect. The rock powder is placed into a tank and mixed into a slurry by adding water. Then, sodium cyanide (NaCN) solution is added to the mix.
The reaction that occurs, the 'Elsner Equation', is as follows:
The water and the oxygen added to the solution during the slurry helps complete the reaction. The gold is dissolved and essentially 'leached' into a cyanide-complex solution. At this point, you now have an aqueous gold solution, with a sodium hydroxide byproduct.
You have your gold in a liquid solution. However, no one wants a watery necklace. The next stage of the cyanidation process is extracting the gold from solution. One of the processes used to remove the gold from the pregnant solution is the Carbon In Pulp (CIP) process (e.g. Cho, Dixon and Pitt, 1979).
This process involves adding activated carbon to the solution. The carbon acts as a sponge, adsorping the aurocyanide. The loaded carbon is removed and then undergoes elution; desorption of gold cyanide at high temperature and pH. The next process involves electrowinning, which uses electrolysis to separate the cyanide (remaining in solution) and gold (sediment at bottom) (e.g. van Deventer and van der Merwe, 1994). The gold sediment is finally mixed with a little Borax, and smelted, returning in the form of solid gold.
Here is a video on YouTube from NurdRage, showing him dissolving gold at home the same way it is done industrially, on a smaller scale.
You have your gold in a liquid solution. However, no one wants a watery necklace. The next stage of the cyanidation process is extracting the gold from solution. One of the processes used to remove the gold from the pregnant solution is the Carbon In Pulp (CIP) process (e.g. Cho, Dixon and Pitt, 1979).
This process involves adding activated carbon to the solution. The carbon acts as a sponge, adsorping the aurocyanide. The loaded carbon is removed and then undergoes elution; desorption of gold cyanide at high temperature and pH. The next process involves electrowinning, which uses electrolysis to separate the cyanide (remaining in solution) and gold (sediment at bottom) (e.g. van Deventer and van der Merwe, 1994). The gold sediment is finally mixed with a little Borax, and smelted, returning in the form of solid gold.
Here is a video on YouTube from NurdRage, showing him dissolving gold at home the same way it is done industrially, on a smaller scale.
