# Reprocessing Tailings from Mercury Amalgamation



## chawimac (Aug 25, 2013)

Hello,

There is a massive problem in Latin America, and plenty of other places I assume, when Mercury is used to amalgamate with gold in the artesanal gold mining. The places I have seen, tailings are discarded into streams and rivers. These tailings contain lots of mercury polluting the environment, but also contain serious amounts of precious metals.

Currently miners get from 4-35 grams per ton of ore. The ore is ground and mercury is added. Tailings are dumped. I will post some pics and videos for your entertainment and education. I would like to reprocess these tailings to remove the mercury and dispose of them appropriately. I figure with the gold that is contained in the tailings it should be economically feasible to clean them up. I personally fire assayed the tailings and found that the valuables in general are 8-15% Au and the rest is silver. Assays varied from 2-4 ounces per ton. Seems very high, and higher than what miners are recovering themselves. Maybe my fire assays are off, maybe miners lied about their recovery, or maybe I interpreted wrong what they recover.

Does anyone have any experience with processing tailings that involves any process other than Cyanide Leaching? Cyanide is highly regulated and would be impossible to import unless you own a mine. Mercury itself is illegal but gets smuggled in from wherever possible.

Attached are some technical aspects of the tailings:


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## chawimac (Aug 25, 2013)

Here are some pics.


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## chawimac (Aug 25, 2013)

More pics.


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## chawimac (Aug 25, 2013)

More pics.


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## FrugalRefiner (Aug 25, 2013)

Without prying too much, may we know approximately where this is? Latin America and my house don't give us much information about your location.

Dave


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## chlaurite (Aug 25, 2013)

The easy part: Recovering *most* of the mercury, and the gold amalgamated into it. It concentrates just like placer gold, so you can pan it, sluice it, trommel it, dredge it, etc. Then once you get it reasonably concentrated...

Distill it. Technically you want a good high quality glass retort, but in practice, you'll recover 95+% of the mercury with just about any still made out of non-metal.

The hard part: What do you _do_ with the mercury you recover?


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## chawimac (Aug 25, 2013)

FrugalRefiner said:


> Without prying too much, may we know approximately where this is? Latin America and my house don't give us much information about your location.
> 
> Dave



Nicaragua


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## chawimac (Aug 25, 2013)

chlaurite said:


> The easy part: Recovering *most* of the mercury, and the gold amalgamated into it. It concentrates just like placer gold, so you can pan it, sluice it, trommel it, dredge it, etc. Then once you get it reasonably concentrated...
> 
> Distill it. Technically you want a good high quality glass retort, but in practice, you'll recover 95+% of the mercury with just about any still made out of non-metal.
> 
> The hard part: What do you _do_ with the mercury you recover?




Any better ideas?


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## chlaurite (Aug 25, 2013)

chawimac said:


> Any better ideas?


Out of curiosity, do you mean that placer recovery won't work for you,
or that distilling it doesn't count as an option,
or that 95% counts as too little?

FWIW, you don't actually need to "boil" it - It evaporates readily well below its official boiling point of 630F (and if you can do it in a vacuum, all the better).


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## chawimac (Aug 26, 2013)

chlaurite said:


> chawimac said:
> 
> 
> > Any better ideas?
> ...



I am not convinced of a 95% recovery. Many of these processors use sluice boxes already. If gravity separation is being effective I would not be getting such a high assay. 

Also most of the small ore processors run at least 10 tons a day, I counted 97 processors in one particular area. My concern is that the scale needed makes your recommendation a bit impractical.


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## butcher (Aug 26, 2013)

With most gold mining or recovery processes there can be lose of values, and depending on how the operation is done and the state of the ore, the process used and how effective it is for a particular type of ore, and even if the process is done properly, these loses can vary with the operation.

Mercury will amalgam with fine gold, but much can depend on how the mercury was prepared, if the mercury was not properly prepared the almagam process will not work that well, also the state of the gold and how these are used, even with the use of clean copper sheets coated with distilled mercury, miners would have loses of both mercury and gold, and with just mercury dumped into ore and mixed or added into the sluice box, there will be lose of both gold and mercury, with oxidized or dirty mercury these loses can become excessive, it will not pick up the gold very well and amalgam with it well, the process of keeping the gold and mercury from flowing out with the tailing's is important for controlling how much gold is lost, there will always be some lose.

This is my thought on trying to recover the gold or mercury from the loses you notice in these tailing ponds.

You may be able to recover some value, but to do it properly would most likely cost you more than the gold is worth, and you will be taking a chance of polluting the environment even worse by attempting to recover the gold, if it was not done properly, I do not see an easy way to do this without putting more mercury pollution into the air or into the peoples drinking water supply, and still make a profit, or make the gold worth the risk, gravity methods you will stir up the mess you will also have lose going into someones water supply, heating the material without distilling it would put mercury into the air which would contaminate everything this air came into contact with for many many miles around, you could make the matters worse and not gain much from it in value.

Retorting or distilling of all of the material in the tailing pond would cost much more in fuel and equipment, than the gold would pay for, and leaching the retorted material would cause its own set of problems for the environment.

I would forget about stirring up these toxic tailing ponds.
And concentrate my time and study on better methods of mining and getting the gold out of the ore without the use of mercury.


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## Traveller11 (Aug 26, 2013)

I would contact the people at Knelson Concentrators in Langley, British Columbia, Canada. They manufacture a line of centrifugal concentrators that will process as much as 45 kilograms per hour right up to massive units that process many hundreds of tonnes per day. These units are capable of recovering gold particles only a few microns in diameter. The prices of these units are a bit high but, if you can get a confirmation on your fire assay of 2-4 ounces of gold per tonne of tailings, I believe it would be a paying proposition for you to purchase one of them.

I do not know how these centrifuges are at recovering mercury from tailings. However, considering mercury's high specific gravity (13.5) and its liquid state, I should think it would be just as easy, if not easier, to separate it with a centrifuge as it is to separate gold and other precious metals. The engineers at Knelson would be able to tell you all of this. Once concentrated, along with the gold, you should be able to employ a closed retort to separate the mercury from the rest of the concentrate. If done properly, these retorts will not release mercury fumes to the atmosphere, although it is still not advisable to use one indoors, just in case. What you do with the mercury once you recover it, I do not know. You will, at that point, though, have removed it from the environment, and that is a good thing. Who knows, the day may come when an international agency actually pays someone to remove mercury from the environment. You would then be doubly rewarded for your efforts.

Knelson Concentrators can be contacted in Canada at 1-604-888-4015 (telephone) or 1-604-888-4013 (fax). Their email address is [email protected] . If you go to this website http://www.knelsongravitysolutions.com/page478.htm they have South American dealers listed, as well.

A similar concentrator is made by a company called Falcon and is marketed to artisanal miners worldwide as the I-Con gold concentrator. It can be seen at this website http://www.iconcentrator.com/

Good luck with your venture!


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## rickbb (Aug 26, 2013)

From what I've seen on various documentaries on this, most of the operations there are illegal or very low budget. They only use the Hg after the gold bearing material is concentrated, they recover this amalgam and boil off the Hg leaving the gold it collected. They never check to see if they left any gold behind in the concentrates before dumping it out along with any Hg leftover.

That may be why you see high values.


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## chawimac (Aug 26, 2013)

Traveller11 said:


> I would contact the people at Knelson Concentrators in Langley, British Columbia, Canada. They manufacture a line of centrifugal concentrators that will process as much as 45 kilograms per hour right up to massive units that process many hundreds of tonnes per day. These units are capable of recovering gold particles only a few microns in diameter. The prices of these units are a bit high but, if you can get a confirmation on your fire assay of 2-4 ounces of gold per tonne of tailings, I believe it would be a paying proposition for you to purchase one of them.
> 
> I do not know how these centrifuges are at recovering mercury from tailings. However, considering mercury's high specific gravity (13.5) and its liquid state, I should think it would be just as easy, if not easier, to separate it with a centrifuge as it is to separate gold and other precious metals. The engineers at Knelson would be able to tell you all of this. Once concentrated, along with the gold, you should be able to employ a closed retort to separate the mercury from the rest of the concentrate. If done properly, these retorts will not release mercury fumes to the atmosphere, although it is still not advisable to use one indoors, just in case. What you do with the mercury once you recover it, I do not know. You will, at that point, though, have removed it from the environment, and that is a good thing. Who knows, the day may come when an international agency actually pays someone to remove mercury from the environment. You would then be doubly rewarded for your efforts.
> 
> ...




Many thanks!


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## rusty (Aug 26, 2013)

chawimac said:


> Traveller11 said:
> 
> 
> > I would contact the people at Knelson Concentrators in Langley, British Columbia, Canada. They manufacture a line of centrifugal concentrators that will process as much as 45 kilograms per hour right up to massive units that process many hundreds of tonnes per day. These units are capable of recovering gold particles only a few microns in diameter. The prices of these units are a bit high but, if you can get a confirmation on your fire assay of 2-4 ounces of gold per tonne of tailings, I believe it would be a paying proposition for you to purchase one of them.
> ...



A thread dedicated to home built centrifuge, not s fancy or expensive as Knelson or the Falcon. http://goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=16975&hilit=+centrifuge


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## iatenorio (Mar 5, 2014)

It is funny I find this topic of Nicaragua Tailings. I just finished working for a company that processes tailings for gold recovery, and there are many other companies to come.

A Canadian one is one that will surely have great success: www.gleneagleresources.com . Also, there are several American and Nicaraguan companies that intend to do "mobile cleanups", or in other words, reprocess as much tailings one site, then move to the next

I have done studies on how many tailings there are, artisanal mills, tailings dumped per day, Au/Ag Hgc content etc.. and the business is pretty lucrative. The problem now is, not how you will recover it, but WHO will recover it. People have found this to be a very good business.

The company I just left (I will now do gravimetric processes in a friends' mine) and trommels in river gold. 

We did try falcon/knelson concentrators, but they didn't work well with tailings with mercury. A Falcon SB150 to be exact.

The process that needs to be/will be implemented, is going to be with cyanide. (agitation). Merrill Crowe to be exact.

The Nicaraguan government will allow it, as long as you will have a secure tailings pond.

If anyone needs advice on this, let me know. Glad to help.

By the way, for the person who took the pictures, in what city was this?




rusty said:


> chawimac said:
> 
> 
> > Traveller11 said:
> ...


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## jimdoc (Mar 5, 2014)

Chawimac's last visit to this forum was;

Last visited: Mon Oct 07, 2013 9:07 am


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