Separating gold from rock ore is a multi-step process that involves grinding the rock ore, creating a liquid solution, including additives to cause the gold to precipitate out of the solution and gathering the gold. After the gold is separated from the ore, it is further refined to remove impurities. Gold found in thick veins is economically easy to separate from the rock ore independent of the price of gold; however, gold particles found in large rock ore deposits are only economically feasible to separate when the price of gold is high.
Separating Gold from Ore
Grind the ore. Transport rock ore from the mine site to a mill. At the mill, the ore should be ground to create sand-sized particles from the ore. The sand will be composed of gold particulates and other useful metals, dependent upon the geologic formation from which the rock ore was found.
Mix the ground rock with liquid. A liquid mixture is necessary to begin frothing to induce the separation of gold from other material. Adding liquid is the first step in the process, but a frothing agent must be added to cause the mixture to create a foam. Productive frothing agents are amyl alcohol, camphor, phenols, gas tar and even essential oils.
Add a collection agent to the frothing mixture. The collection agent bonds with the gold particle and forms an oily film that collects onto the air bubbles used for frothing. This technique is also known as flotation because the gold "floats" above the liquid. Productive agents belong to the n-alkanol chemical family and include include n-butanol, n-pentanol and n-hexanol.
Add organic chemicals to the mixture. These chemicals prevent other contaminants, originated in the rock ore, from adhering to the air bubbles. A productive organic chemical addition is carbon, to which the other contaminants will bond, leaving the gold to adhere onto the air bubbles.
Aerate the liquid solution and then separate froth from the water bath. The froth contains the gold particulates that will be further refined to remove impurities. The gold concentrate floats on top of the bath, but in a separate cell for easy collection. The water bath is collected from the bottom of the cell. After collection, cyanide can be added to further refine the gold to remove impurities, such as sulfides; or the gold concentrate can be heated in a smelter and the molten metal poured into molds for shipment.