Mercury is associated with free gold recovery from mineral concentrates. The method is as crude as ordinary traditional placer mining and ore beneficiation. However, it was pervasively used until cyanization came into use in the late nineteenth century which is awfully recent.
So it is never a surprise to locate traces of mercury metal around old mining buildings. The only saving grace was that it was good at sinking out of sight and usually found a way to sort of get out of the way.
Making mercury is easier still. Locate a source of cinnabar which is red, and roast it to distill the mercury fumes. Cinnabar is easily identified by the likelihood of minute drops of mercury associated with it. In short, you really have to work in order to not figure all this out.
So it is hardly a surprise that the Indians have been using mercury. Most likely the antiquity of the practice will likely prove out to be millennia. The gold extraction of the Andes was extraordinary and was only plausible if it had been continuous for several millennia.
Of course proving all of that is a bit of a trick for the above mentioned reasons. It really likes to travel and get lost making it difficult to prove associations. Also processing would necessarily be at a remove from any habitation. Toxicity is learned quickly with mercury.
First Evidence Of Pre-Industrial Mercury Pollution In The Andes
by Staff Writers
Edmonton, Canada (SPX) May 21, 2009
http://www.terradaily.com/reports/First_Evidence_Of_Pre_Industrial_Mercury_Pollution_In_The_Andes_999.html
The study of ancient lake sediment from high altitude lakes in the Andes has revealed for the first time that mercury pollution occurred long before the start of the Industrial Revolution.
"We found that mercury mining, smelting and emissions go back as far as 1400 BC," said Cooke. "More surprisingly, mining appears to have began before the rise of any complex or highly stratified society. This represents a departure from current thinking, which suggests mining only arose after these societies emerged," said Cooke.
University of Alberta Earth and Atmospheric Sciences PhD student Colin Cooke's results from two seasons of field work in Peru have now provided the first unambiguous records of pre-industrial mercury pollution from anywhere in the world and will be published in the May 18th Early Edition of the Proceedings of the National Academy of Sciences (PNAS).
"The idea that mercury pollution was happening before the industrial revolution has long been hypothesised on the basis of historical records, but never proven," said Cooke whose research was funded by the National Geographic Society.
Cooke and his team recovered sediment cores from high elevation lakes located around Huancavelica, which is the New World's largest mercury deposit. By measuring the amount of mercury preserved in the cores back through time, they were able to reconstruct the history of mercury mining and pollution in the region.
"We found that mercury mining, smelting and emissions go back as far as 1400 BC," said Cooke. "More surprisingly, mining appears to have began before the rise of any complex or highly stratified society. This represents a departure from current thinking, which suggests mining only arose after these societies emerged," said Cooke.
Initially, mercury pollution was in the form of mine dust, largely resulting from the production of the red pigment vermillion. "Vermillion is buried with kings and nobles, and was a paint covering gold objects buried with Andean kings and nobles," said Cooke. However, following Inca control of the mine in 1450 AD, mercury vapour began to be emitted.
"This change is significant because it means that mercury pollution could be transported over much greater distances, and could have been converted into methylmercury, which is highly toxic," said Cooke.
"All of these results confirm long-standing questions about the existence and magnitude pre-industrial mercury pollution, and have implications for our understanding of how mining and metallurgy evolved in the Andes," said Cooke.
Extracting Gold Using Mercury
Taken from Gold Prospector magazine March, 1995
"I think that if you follow this step by step process, you will find, as many prospectors have, that this is a proven, profitable method for extracting fine gold from concentrates.
Whether you use a gold dredge, sluice box, dry washer, rocker box or most any other type of gold getting apparatus, the concentrates you accumulate in the field should be dumped into five-gallon buckets. Of course, you should pick out all the visible gold then and there.
You should dump the remaining material into the five-gallon buckets and bring them home with you. Even if you have a month to work, don't attempt to set up an operation for cleaning concentrates in the field. Once you get the concentrates home, run them through a poop tube, spinner or wheel, concentrating a five-gallon bucket down to an amount about the size of a quart fruit jar or a three-pound coffee can.
You then put that material into the rock tumbler with some caustic soda (Sodium Hydroxide) and run it for about two or three hours. Add mercury, run another two to three hours. Run the concentrates back through the poop tube, wheel or spinner. Lift out the mercury by inserting a large glob of mercury. Put this into your syringe or your mercury press and squeeze through pure cotton to recover ninety percent of the mercury at this stage.
Deposit the compressed ball of mercury containing your gold into nitric acid in a Pyrex beaker over a hot plate. Let it boil for fifteen minutes. Do this OUTSIDE in a well ventilated area. Be sure you DO NOT BREATHE any of the vapors. Dump that material off into a water-baking soda solution, rinse with clean water and remove the fine gold. Insert a copper rod overnight in the acid waste before disposing of the solution.
This, my friend, is a method for making money each and every time you go out."
BE CAREFUL!! I have found that a 50/50 acid and water solution works well and makes it more cost effective.
Start out with a cold acid solution with the cotton ball in it. Then bring it to a boil. Wear rubber gloves when handling mercury and do not smoke.
After you have experimented with this method, the most cost effective way to use the mercury is to run large quantities of concentrates at one time.
You can also run small amounts and put the mercury back in a used mercury container until the mercury is full of gold. Mercury amalgam will hold two to three times its weight in gold. When the mercury is full of gold, it will look thick and dull in luster.
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