The oxidized mud is then transferred to the carbon leach circuit to dissolve the gold from the rock. This is done via gravity-fed tanks and chemicals like sodium cyanide. Sodium cyanide extracts gold from rocks and turns it into liquid. This process can take days! By the time the rock particles reach the last reservoir (this takes several days!), almost all the gold is recovered.
At the same time, activated carbon (coconut husks) is pumped upstream through the tank system to recover the leached liquid gold. Once full of gold, the carbon moves to a gold desorption column designed to remove the gold from the carbon.
Once this process is complete, all that is left is an eluate containing hot water, gold solution, cyanide and caustic soda. The eluate is transported to the gold room and deposited by electrolysis on cathodes wrapped in steel wool.
The steel wool is then melted in a furnace and causes the gold to sink to the bottom and the remaining waste (slag) to rise to the top. As the bar is cast, the slag flows out, followed by the gold, causing the slag to overflow out of the mold, leaving the gold behind.
And finally, we have our gold bar!
A sample is taken and sent to the State Mint to determine quality before the gold bar is then removed and cleaned. It is weighed and numbered before being sent to the Mint.
So this is it ! The long and incredible process that people in the gold industry use to bring this precious mineral from the ground to the mint.