We all know that we get gold from gold mines. But, have you ever asked yourself how? How do we get the gold from earth, separate it, shape it then wear it or keep it?
The first thing you need to know is that it doesn’t come out as chunks from the mine. It undergoes a lot of serious processes to become the refined gold we see.There are three main processes that separate gold from other minerals. Cyanide leaching, mercury amalgamation, and cornstarch…yup, that cornstarch.Cyanide leaching is considered as the most popular process that most companies use. It goes as follows: you prepare a liquid solution of cyanide, crush the rocks
you believe contain gold and turn it into a powder, slurry if we can give it a name.Then add lime to your slurry to increase its PH levels, make it more alkaline, so it won’t release any cyanide toxic gas when the cyanide is added to it. After that,
add the slurry to the cyanide solution, and wait for the magic to happen.The gold and silver in the slurry form a metal-cyanide complex. An oxidization process must be applied, by adding oxygen or a per oxygen compounds, to increase the leach rate. Finally, activated carbon is added, to absorb the metals and form them into lumps. A second process is carried out on those metal lumps.They are dipped again in a cyanide solution to separate the metal from the carbon. The carbon is then recycled, and the solution is put in cells where they pass a strong electric current through it to separate gold from silver. This process is called electro winning. By electro winning, the gold is collected on the negative electric terminal. It is a lot of work, but some manufacturers believe it is worth it.It is also very harmful to the environment, because of the toxic fumes that are released from the cyanide solutions.The second method, the mercury amalgamation method is a lot easier than cyanide leaching. The secret to this method is that gold and mercury are best friends. Whenever mercury is added to an ore, gold and mercury quickly unite in an alloy. In order for that to happen, the slurry must be squeaky clean. So, they
wash it in nitric acid first. Slurry and mercury can be mixed together in many ways. one way is to put mercury in the bottom of a pan, add water and the clean slurry to the pan, heat it up, then quickly, gold is absorbed to the mercury and they form an alloy together at the bottom of the pan. Mercury is then removed from the alloy either by heating or by sulfuric acid. This way is also very harmful to the environment.As the harmful effects of both cyanide leaching and mercury amalgamation on
the environment caused pollution, scientists had to find a better, greener solution. By chance, a scientist named Zhichang Liu discovered that alpha-cyclodextrin sugar, which is extracted from cornstarch, can be efficiently used to separate gold from other minerals. As a result, in 2010, some European countries such as Germany, Czech Republic and Hungary banned the use of cyanide leaching in gold processing, and instead applied the cornstarch method. Most European countries are going to follow in the footsteps soon.