other amalgamation processes were later developed, importantly the pan amalgamation process, and its variant, the washoe process. the silver separation process generally differed from gold parting and gold extraction, although amalgamation with mercury is also sometimes used to extract gold.
though successful in extracting gold-rich minerals, the widespread use of the process resulted in extensive environmental damage, such as increased flooding and erosion, and sediment blocking waterways and covering farm fields. these problems led to its legal regulation. hydraulic mining has been used in various forms around the world.
the amalgamation process used to extract the gold from the crushed ore was relatively inefficient and largely contributed to decline. by 1893 the new macarthur-forrest process used for gold extraction brought a short-lived revival in the klerksdorp gold mining industry, but uncertainty created by the jameson raid of december 1895 as well as .
gold parting as a process was specifically invented to remove the silver. the main ancient process of gold parting was by salt cementation and there is archaeological evidence of that process from the 6th century bc in sardis, lydia. in the post-medieval period parting using antimony, sulfates and mineral acids was also used.
hydrometallurgy is concerned with processes involving aqueous solutions to extract metals from ores. the first step in the hydrometallurgical process is leaching , which involves dissolution of the valuable metals into the aqueous solution and or a suitable solvent.
in order to maximize gold extraction, mercury is often used to amalgamate with the metal. the gold is produced by boiling away the mercury from the amalgam. mercury is effective in extracting very small gold particles, but the process is hazardous due to the toxicity of mercury vapour.
gold heap leaching. heap leaching is an industrial mining process used to extract precious metals, copper, uranium, and other compounds from ore using a series of chemical reactions that absorb specific minerals and re-separate them after their division from other earth materials.