Small Scale Treatment of PM Sulfide Ores

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Reno Chris

Well-known member
Joined
May 5, 2011
Messages
274
There is no one universal way of treating sulfide rich precious metal ores - in the mineral kingdom there are all sorts of complex minerals which contain, in addition to gold or silver, complex combinations of lead, zinc, copper, iron, nickel, manganese, palladium, mercury, antimony, arsenic and others. In addition to sulfur, one may also have ores with selenium, tellurium, and others. Gangue minerals are not just quartz and calcite, but may include a whole host of fluorides, oxides, sulfates, chlorides, silicates, etc. The point is that sulfide ores can be highly variable.
You can see that with sulfide ores, there are a million and one possibilities and while some types can be treated similarly, there are many different categories or types. There can never be a one size fits all approach. We can all wish for rich free gold ore! With that stuff, you just crush it up, pan it out and melt to make a button (or refine it if you like). But sulfides are another story. You need to convert whatever metals you have from mineral to metal, and do it without making a big mess, and without a big stink of sulfur dioxide and smoke to offend your neighbors, either. This is not necessarily easy. Then once converted to a metallic state, you must still separate the precious metals from the base metals. This is why the old timers had such difficulty with these ores and in many places simply gave up when the mines worked their way down to the sulfides. Rebellious or refractory ores they were called.
I have about 200+ pounds (roughly 100kg) of rich silver gold ore that runs roughly 3 ounces per ton of gold and 70 ounces of silver. On that basis, my 200 pounds should contain about 0.3 ounces of gold and 7 ounces of silver - but I know that I won't get 100% recovery. There is also considerable iron, zinc and lead present, with some minor copper and very small amounts Antimony and Arsenic. All these elements are in the form of sulfides and complex sulfides (except the gold which is mostly free in tiny particles). I am not kidding myself that this is some money making scheme. It's a demonstration project to prove I can do this - though I will make a few bucks, just not much when you consider the time invested. The output of PMs will far exceed the cost of reagents and fuel, but I figure I will be getting less than 50 cents an hour for my time and one can hardly consider that as a way to make good money. I will have expensive equipment in use from crushers to furnaces to lab ware and acids. If I could buy a shaker table I could run the cost up by a few thousand, but I just can't justify that expenditure at this point.
This is going to take some months to accomplish, as I will only be working on it off and on. I will take photos as things as they progress and share them here. My goal is to recover 10 to 15 grams of gold, 7 to 10 ounces of silver, minor copper (perhaps a few ounces) and a number of pounds of lead (the lead will be used to cast bullets). I may also attempt to recycle the zinc and copper I consume in the Parkes and silver cementation steps. Disclaimer - this is not intended as a full "how to" type of lesson with all the process details and necessary safety precautions clearly spelled out. I am sharing my efforts with the forum so you can see what is involved. If you attempt something like this yourself, you will need to possess the necessary mineral processing expertise on your own and understand all the dangers involved and know enough on your own to take all the necessary safety precautions. I am not offering to serve as anyone's consultant. A good description of the steps I will use are as follows:
1. Crush the Rock.
The rock cannot be processed as large chunks and cobbles - the form it is in now. It must be crushed to a powder to process. I have 2 crushers and will take the ore down to minus 20 mesh. Yet even before it can even be run through my crushers, I will need to break down the larger pieces by hand with a 2 pound hammer. I will have a dust collection system for the crusher operation which I will show (it will use a shop vac unit I have).
2. Reduce the bulk of the ore.
My 200 pounds of ore is a lot of rock to deal with. I will concentrate it down to the heavy components. Sulfides are generally dense minerals and gold is as well, so I will concentrate using a specially made sluice system. I wish I could use a shaker table, but these are several thousand dollars to purchase, an amount much more than I want to spend on this project. Yep, I will lose some, but I do not have infinite monetary resources. The ore has a 5 to 10 percent sulfide content, so I expect about 10 to 20 pounds of sulfide concentrate. Dealing with 10 to 20 pounds is a lot easier than 200 pounds. There will be some loss of values in this operation - but I accept this because although the method is less than optimal, it's the best I can put together.
3. Perform a series of giant fire assay fusions.
The sulfides contain some galena (lead sulfide) but not enough lead to serve as collector for a full fire assay on that material alone, so I will add some other galena from another source (which also contains some good silver, but very little gold) and some Litharge (plus a bit of charcoal to help reduce the litharge). I will add a good amount of sodium carbonate and borax to form a flux. I will perhaps, also add some crushed glass as well to make sure there is enough silica to form a decent slag cover on the molten sulfide matte and maybe even a little crushed fluorite as well. The old assay trick of using scrap iron (normally nails) to reduce the molten galena will be used. THe formula is: PbS + Fe = FeS + Pb The reaction is driven because Fe is a more chemically active metal than lead (silver and copper are also displaced as they are less active than iron). I will carefully stir the whole molten mass with an iron rod (while the crucible is still secure within the furnace to be safe). The lead should capture the PMs, and when I pour the whole mass into a cone mold, I should get three products - a slag glass, a sulfide matte of mostly iron sulfides, and a lead button. I will use a large crucible and hope to process around 3+ kg of total material (flux + scrap iron + extra galena + sulfide ore concentrates) in each charge, with resulting a lead button of roughly around 1 to 1.25 Kg in size each time.
The assay fusion will be done with a propane furnace out in the desert, in a fire safe location where odors and smoke not will harm or offend anyone. I also will use a mask with a HEPA filter to make sure I do not breathe any hazardous smoke. It may take 4 to 6 or so charges and pours to process all the concentrates from step 2. The lead will be retained and saved for step 4.
4. Perform a Parkes Process capture of the copper, gold and silver.
On completion of the assay like fusion reduction process, I should have 5 to 8 Kg of gold, silver and copper bearing lead, which I will melt and mix with a couple pounds of zinc and stir. I will not take the mix up to a high temperature to try to dross out the copper, I will just collect the copper with the zinc and separate it later (there should not be much copper anyway). I read a thread on this forum where a member used a motor to create stirring for the necessary surface contact for the migration of the PMs and copper into the zinc. I will just stir for a time by hand with an iron rod. At the conclusion, I will pour off the material into a cone mold and after separation, I should have a low PM lead metal suitable for bullets and a few pounds of PM bearing zinc alloy.
5. Part the zinc from the gold, silver and copper with Hydrochloric Acid
It may be that for use of Hydrochloric, inquarting may be necessary, but I will try without doing so first. When complete, I should have zinc in solution and the copper, gold and silver as an insoluble black powder. I will wash the powder well with warm water. I may attempt recovering the zinc by electrolytic methods - I should be able to get most of the zinc out.
6. Part the gold and silver with nitric acid
The silver and any small amounts of copper present will be soluble in plain nitric, and I will cement out the silver with metallic copper, then recover all the copper electrolyticly. I will then pour the silver into a fairly pure button and the gold and final nitric insoluble materials into their own button and at that point the final extraction process will be complete. The gold will not be .999, but it should be maybe 90+ which will be good enough for my purposes.
 

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I took a tour of the Comstock many Years ago. One of the features was a pothole in the floor of the tunnel where an enormous amount of Gold and Silver had settled. The chunk of Ore that I took for a souvenir was a soft Talc with finely dispersed Pyrite. Never did process it, though.
 
is -20 mesh small enough particles? I would think that even smaller particles would be easier to extract from, something closer to the -200 mesh size coming out of a ball mill or rod mill, both not as hard to build as one might think, and if you have enough ore, i wager you could talk someone who has a smaller ball mill sitting, to make a run or two for your testing....


William
Idaho
 
Remember that -20 means that all of the ore is less than 20, but the majority of the ore will be maybe 100 mesh, with plenty being smaller.

-200 mesh means all the ore is smaller than 200 mesh, with probably lots being around 400 mesh. There is such a thing as being too small, rendering the ore into a clay like state that is hard to treat - even if you are leaching with cyanide. One of the reasons stamp mills are no longer used to crush ore is that they made too much slime - that actually reduced recovery.

So for what I am doing - recovery by gravity only - yes, 100% minus 20 mesh is about right.

Chris
 
your crushing milling goal should be 80% passing -200 I have made a ball mill that can do about 300 lbs an hr. since you have a sufide type ore you should be looking at processing via a floatation cell or column . I will not try to convince you as to method but id you look up someing caled the (75 ways of gold concentrating) your answer will almost certainly be there. Its the best info on methodes for finding grind size for each way od slucing or floating ore. good luck Bryan in denver [email protected]
 
Chris...

I reviewed some simple techniques small mining operators were using in poorer countries that may assist in your thinking on the sluice type you build.

It consists of a long wooden sluice placed at about a 10 degree angle that was fitted with tight nit wool shag carpeting. The miners would ground their ore to a fine powder then run a moderate flow of water down the sluice, mixed with the fine powder. the heavier metallic particulates would sink into the carpeting while the lighter minerals would was away. They'd let the silt flow out then take the carpeting up from the sluice and place it into a tub of water then basically wash the carpet in it, capturing all of the heavier metallic particles and then panning it. perhaps that may help...

Something I did awhile back that I've been recently pondering on is another possibility, IDK though perhaps you can try this and see if the results turn out like I suspect they did for me. I powdered my ore then set it to slow roast for about 2 hours at roughly 300 F. - mixing the contents every now and again then placing the contents into a warmed coffee pot then shocking it with muriatic. the greyish/ silverish material that began floating on the surface of the muriatic after it got through sputtering and steaming appeared to be a lead/ silver concentrate with gold flecks within it... as the image below shows in some small detail. I didn't have a chance to continue the experiment however...chalco-plumbo-hcl-shock.JPG
 
Richard,

I tried a similar process to the muriatic bath you used, but on an arsinide type silver ore. I experimented with this to remove the calcite from the ore before treating it with nitric to remove the silver. It totally flopped and I have never bothered with this again. All I did was pollute this ore with chlorides making it difficult to treat with nitric acid. Win some lose some. Here's the similarity to yours. The frothing, boiling action of the muritac did float to the top the same silver "scum" . I collected just over gram of this from the surface of my bucket, washed and cleaned it. It dissolved in nitric, then immediately turned to silver chloride. So yes, you have floated some silver to the top. Totally inefficient for recovery. But, now you know it's there.

I am following this thread very carefully, as I have just brought home from Northern Quebec a few hundred pounds of sulphide type gold ore. So, this one's really got my attention. Hope this info on your silver froth helps.

Rob.
 
Thanks for the validation on your result torscot as it comparatively related to mine. I never thought to follow through with this though because at the time I was involved with a metallurgist who has a fairly equipped lab. He and I went our separate ways when i'd discovered he'd been fudging every ore test we'd done so that he could go back when i wasnt around to retrieve the lost PM/ PGM values from his firebrick walls and used cupels. he'd purposely overfire our tests with them for the most part failing to provide a result or if one appeared it was relatively minute compared to what the filtration promised... point in case look at the coloration on this cupel and understand that the reason why it's bright red surrounding the test reslt button is that a majority of the valued sank into the cupel material with the lead.

production-assay.JPG

It really sucks when you're sitting on a substantially life changing property and all you want is for someone to actually be honest enough to help you develop it into that life changing result...

If you're truly into processing the gold sulphide ores that you say you are from what you've managed to collect from Northern Quebec i'd like to invite you to consider taking a trip down here to Las Vegas and We can spend some time putting our heads together on some rather high value ore types I'm absolutely positive you will become a giddy as the kid in a candy shop over...

Review this forum for a rather comprehensive look at exactly what it is I'm talking about... Cheers!

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=44&t=8709
 
Just wanted to say I found this to be an interesting thread though I don't work with any ores any more(& haven't for a long time) but I do hope to again in the future so have been keeping an eye on this thread & hope more will be added as time goes on

Kurt
 
DarkspARCS said:
... point in case look at the coloration on this cupel and understand that the reason why it's bright red surrounding the test reslt button is that a majority of the valued sank into the cupel material with the lead.


If the resulting lead prill from the preliminary assay fusion were scorified to remove the impurities as it should have been, then there wold not be any precious metal loss to the cupel, and neither would the cupel be that color, nor would it have a dark base metal contamination ring, which this cupel definitely does have.

As an assayer I know that much, and can definitely tell that the lead prill was not scorfied before cupeling it to recover the precious metal values contained within it that were recovered from the ore in the fusion process.

The contamination is copper that caused the color impartation to the cupel,
and being that you and I are familiar with your ore, we know that to be an absolute if it were not removed before the cupeling process.

Give me a call and I'll privately share some leaching knowledge with you. :p
 
I'm having similar problem and thinking about making small shaker table with use of laboratory orbital shaker like this one https://www.thermofisher.com/order/catalog/product/SHKE3000

not sure about what kind of platform to put on top of it.
thanks
 
I cant believe that its been that long - I've made more plans and done only a little. toward moving this to reality.

I really need to work on this, hopefully when the weather here improves.

Also, I now plan on doing a full Youtube video of the entire process.
 
Reno Chris said:
I cant believe that its been that long - I've made more plans and done only a little. toward moving this to reality.

I really need to work on this, hopefully when the weather here improves.

Also, I now plan on doing a full Youtube video of the entire process.

Hi Chris

Per the underlined - VERY much looking forward to the video 8) :!:

Kurt
 
Well, the first video, hopefully to be completed in the next couple months will be a 3 part "Rock to button" video on taking gold bearing quartz, breaking it up, crushing it, concentrating the free gold using a recirculating sluice and then taking the free gold concentrate and pouring a gold button.

I can do all of the above at home. Part of the problem with the sulfide project is the smelting the sulfides down to lead containing the silver and gold. That has to be done at a remote site. I cant do that in my backyard as I'd have a dozen neighbors calling to complain about the smoke and sulfur odors. I will be kicking pounds of sulfur dioxide up into the air. So I will pretty much need to make a trip out to the middle of nowhere just for the purpose of doing the smelting part of the process.

I'll try to do these videos this summer and post notice here on this forum.
 
I know the place. On Rt. 50 in Nevada there's a sign pointing North and South at an intersection that says "Middle of Nowhere."
 
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