An amalgam is any combination or mixture of mercury with another metal or with an alloy. Most metals are soluble in mercury, but some; such as in the case of iron are not. Amalgams are commonly used in dental fillings.
Mercury has been used in the gold and silver mining methods because of the convenience and easiness with which mercury will amalgamate with them. In gold placer mining, in which minute specks of gold are washed from sand or gravel deposits, mercury was often used to separate the gold from other heavy minerals.
After all of the practical metal had been taken out from the ore, the mercury was dispensed down a long copper trough, which formed a thin coating of mercury on the exterior. The waste ore was then transferred down the trough, and any gold in the waste that was amalgamated with the mercury. This coating would sometimes get scraped off and refined to get rid of the mercury, leaving behind somewhat high purity gold.
Mercury amalgamation was first useful to silver ores with the development of the patio process in Mexico in 1557. There were also additional amalgamation processes that were created for processing silver ores, including pan amalgamation and the Washoe process.
Today, mercury amalgamation has been changed by other methods to recuperate gold and silver from ore. Hazards of mercury toxic waste have played a part in the very close to disappearing of mercury amalgamation processes. However mercury amalgamation is still regularly used by small-scale gold placer miners, in particular in developing countries.
If you are considering getting into the prospecting business in a more serious way, you will probably not be content with just scooping up gold flakes as it is a process that takes a lot of time to do and you are probably thinking you could be using your time to get to the real deal. Once you have already mastered beyond the art of gold flakes, which means that you have probably already gotten used to using a sluice or a rocker instead of a pan, you will need to start amalgamating the gold, and then recover it.
Something important to know about mercury is that it is dangerous. Most of the places or people that work with mercury are the large scale miners. Only about .01 mg in a human’s body can cause death. Unfortunately after mercury has gotten into the body of a human, it cannot be taken out.
There have been some undocumented reports of some serious fines due to the usage of mercury in state and federal recreation areas because it can be very dangerous if it gets lost in the environment. If you do find this, the best thing to do would be to save the concentrates until you have a good amount of them and then give the job to someone who has experience at it.
For those that are interested in amalgamating their own gold, there is a way to do this:
Put a little drop of mercury, this can be the size of a pea, inside a container with a wide mouth, or any other thing you are using to store you concentrated gold and sand mixture in. remember to not place the mercury inside your prospecting pan as this will lead you to end up with a thin coat of mercury all over the bottom of your pan which you will then need to scrape off.
You should move the mercury around in the bottom of the container that should not have a lot of water in it. This will cause the gold to dissolve in the mercury and it will form what is known as an “amalgam”. This will not cause the sand to dissolve though. After all of the small flakes of gold have been taken up by the mercury, it will have a yellowish color to it and will look a bit bulgy and droopy.
In the past the prospectors used to use a little chamois bag in order to get the gold out of the mercury by squeezing it out. You can do the same by putting the mercury in the bag, tie it up and then squeeze down from the top. It will help to twist the bag a little bit. This will cause the mercury to come out of the chamois bag and will leave the bottom of the chamois bag with mostly gold, however it will still have some mercury in it. You can get rid of the rest of the mercury by heating the bottom very slowly over a pan on low heat for around half an hour.
Important health notice: Mercury and the fumes it lets off are poisonous. If you are going to be doing any sort of heating operation with it, make sure this is done out in the open, that no children are around, and make sure to not inhale the vapor. After you use a pan to vaporize the mercury do not by any means attempt to use the pan for cooking afterwards.
Another way this job was done in the past was by using a white potato. Old time prospectors used to cut the potato lengthwise and then they would scoop out a little hollow in one half of the potato and put the drop of mercury amalgam in it. They would then bake this for about one hour more or less over a slow bed of coals. This would cause the potato to absorb the mercury and would leave a small bottom of gold on the potato.
After having used a potato for absorbing the mercury make sure to get rid of it by burning it or burying it. do not leave it anywhere near reach of children or dogs.