# Smelting high sulfides Gold concentrates



## Jimijoe (Oct 25, 2015)

New to the forum, thank you for you help. I have high sulfide ore from Colorado, I roasted my cons for 3hrs, I ran a magnet thru the cons, I mixed 40g of my ore with 120g of standard flux from Action Mining. Heated my oven to 1900 degrees, let it there for 30 minutes. Than poured it into a cone mold, out pops the lead button, I broke off the glass and put the lead in the Kepel at 1750 degrees for 45 minutes. Here's where I got lost, so I take it out of the oven and there is a button in the Kepel the size of a nickel. Since it was so big I thought that it needed more time in the oven so I put it back in the oven for 15 minutes. I open the door to see the button, it looks a little smaller, so I tooked it out of the oven, when I went to pick up the Kepel it comes a part. So I pick up all the pieces and put it back in a new kepel and put it back in the oven, waited a half hour, took it out and no button, just scrap from the broken kepel. So I'm confused about where my Gold is at. I'm using the same cons that I sent to 2 of the biggest Assay companies in the usa. Both Assays came back at 6.oz per ton. So there should be a gold button in that kepel. Can someone give me some direction. What am I missing. Thank you, jim


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## Palladium (Oct 25, 2015)

So what's the math on the return for 40 grams say should be there?


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## Jimijoe (Oct 26, 2015)

I'm not totally sure, but there should be something in the kepel.


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## Platdigger (Oct 26, 2015)

Well, if my math is right, just over 8 milligrams.
I read that with some high sulfide ore assays the flour is omitted, and from one to four nails added.
The nails serve to reduce the litharge to lead, as well as reduce the sulfides.

Oh, and the spelling is cupel.


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## Jimijoe (Oct 26, 2015)

Well I'm trying again tonight, I'm measured out 29.6 gm of roasted demagnetized cons and mixed in 90g of standard ore flux. Set my oven at 2000 degrees and let it in the oven for an hour. Than I removed it and poured it in a cone mold, let It cool and hammered off the glass. The slag looked nice and shiny. I than took the lead and put it in a cupel at 1750 degrees for about 1 hour, then I took it out to see what's in the cupel, I got a very small pin head bead, it's so small I dont think I can even weigh it. No gold,


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## Palladium (Oct 26, 2015)

You do realize your talking about like 6 milligrams? That is hard to measure without very precise equipment. It would take about 167 of these test to equal 1 gram.


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## 4metals (Oct 26, 2015)

Generally a sample size of 29.166 grams is used. This is referred to as an "assay ton". What this is, is a mathematical relationship between the avoirdupois pound and the troy ounce such that for every milligram you recover in the cupel equates to one ounce per ton in the ore. 

But even at 40 grams, you are looking for about 8 milligrams or 0.008 grams. That is tiny.

You have to use a cupel large enough to adsorb the lead from the 120 grams of flux you used. Likely the cupel was too small and that is why you had a nickel sized chunk after 45 minutes. Cupels are rated by how much lead they can absorb. How much litharge was in the 120 grams of flux? That is how you know what size cupel to use. Put the chunk in a new cupel and continue on at temperature. 

By the way, 6 oz per ton is very rich ore as ores go. Some of the best mines in the world operate under 1 oz per ton. You are talking about a concentrate I assume. How did you concentrate the ore?


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## 4metals (Oct 27, 2015)

JimiJoe said:


> I got a very small pin head bead, it's so small I don't think I can even weigh it.



Action mining has a chart on page 16 of their catalog that is used to determine an approximate weight of a gold bead by its diameter. I much prefer a balance but this is a rough indicator. At 6 mg (where you should be with the size sample you used) you are looking for a bead 0.035 inches in diameter. That is one small bead. So even having a bead is a positive thing. As a point of reference the head of a pin is said to be 1.5mm or 0.059 inches. So smaller than the head of a pin can still be some decent cons. 

I would take that bead, wrap it in lead foil, and cupel it one more time to make sure it is just precious metals and no clingon junk. It may get smaller but it will be purer.


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## Jimijoe (Oct 27, 2015)

Ok, with being said. Since I had my cons Assaed already, many times! I'm trying to figure out how to smelt my cons in bulk so I can make my own bars. I can't keep making pin head size beads. I have all the crushing equipment, thru the centrifuge, on to my shaker table, next into the oven. I have invested big time in this, my Assays are rich, but at the end of the day, all I get is pin heads of metal. What am I miss here.


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## FrugalRefiner (Oct 27, 2015)

I could be wrong, but if I understand what you've written, you've sent your cons to be assayed, and the assay is 6 oz per ton. If there are 6 oz per ton of cons, all you're going to get from processing small amounts is tiny buttons.

Now if you had the original feed ore assayed at 6 oz/ton, and then you processed that feed stock to get the cons you're trying to process, you might expect more, but that's not how it sounds.

So to get 6 oz, you need to process a ton of cons.

Dave


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## kjavanb123 (Oct 27, 2015)

Hi,

Search the youtube for mbmmllc and there is a great video about smelting sulfides by Jason Gaber. Here I had a chance to find them. These guys are so great at what their do, from their shaker table design and hammer mill to process e-waste, to complete smelting and refining anode slimes.

Here is his video about smelting black sand sulfide. I am sure it can be somehow modified to be used in smelting ICs, or SMDs.
https://www.youtube.com/watch?v=ko608Ti7lcs

Here is the video where he uses electrolysis to get the copper out of anode, and leave the anode slimes.
https://www.youtube.com/watch?v=cnJeK9CwkiU&feature=em-subs_digest-g

Regards
Kj


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## Jimijoe (Oct 29, 2015)

I will look up there videos, thank you very much.


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## 4metals (Oct 29, 2015)

I think the guy who made the video's cons were much much more concentrated than yours. He said he collected 8 grams of gold in the copper as per the XRF result. So how much is a cup (the amount he processed with 2 cups of flux and 2 pounds of copper?) Let's guess there are 4 cups in a pound, correct me if I am wrong, my kitchen skills are nonexistent. So 4 cups is one pound times 8 grams Gold per cup so 32 grams per pound of concentrate. Rounding the 32 down to 1 troy ounce you have a concentrate used in the video of 2000 oz per ton.

That is a world of difference from 6 oz per ton!

What you have is a leaching proposition not a smelting proposition. 

On another note, the kiln he used is very nice and if you go to http://www.govdeals.com and look in the arts and crafts section, there are usually kilns there and very inexpensive.


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## Barren Realms 007 (Oct 29, 2015)

1 cup of water equals .52159 lbs.

Or course copper would weigh a lot more.


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## 4metals (Oct 29, 2015)

So even if it is 2 cups to the pound, the concentration is still 1000 OPT. Hardly in the same class as 6 OPT.


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## kjavanb123 (Oct 29, 2015)

Hi,

Can he just use a blue bowl or any gravity separation equipments to concentrate the materials more then follow Jason Gaber methods? 

Regards
Kj


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## 4metals (Oct 29, 2015)

Well to follow the smelt procedure, which is a viable option if you can get the concentration up to that level of Jason's cons, that will still involve electrolytic copper recovery. And slimes refining. But we all live for that type of thing anyway! 

It would be interesting what method Jimijoe used to get to 6 oz per ton. Depending on what the feed material is and the gold size, sometimes gravity separation passes as much gold off of the table as it concentrates. 

I would like to hear how Deano would approach this. From his posts, he has likely seen something of this nature before. Some more analytics from the OP would be helpful.


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## Deano (Oct 30, 2015)

There is a good reason why the mining industry virtually abandoned gravity separation overnight when flotation became established at the start of last century.

Unless you really know what you are doing on a table you will have heavy losses of concentrates.

Tables concentrate by specific gravity difference between particles of the same size, this is why you will read advice to put a lot of effort into sizing the feed and running only a tightly sized feed.

The biggest problem with sulfides is that they tend to slime when milled.

All sulfide ores will respond differently to milling, some will have the sulfides liberated at a coarse grind size, others will need fine milling to achieve liberation.

Most small scale miners have neither the equipment nor the expertise to get good gravity separation on a sulfide ore.

Those that can get good separation either have an ore which has sulfide liberation at a coarse milling size or they accept that they have to mill fine and put the milled product over the table at a very slow feed rate.

If you are serious about concentrating the ore then the above are your gravity options.

It is possible for a small scale operation to run a flotation cell on the milled material and get a higher grade con with less losses.

Second hand small cells are available and if you have a competent operator set it up and show you how to trouble shoot you should be able to run the cell yourself, it is not rocket science.

Getting to the assay problem, the calculations presented by members are correct, you are looking at a very small bead for 6 oz cons.

Doing your own fire assays is problematical until you have a fair amount of experience.

Some of the problems in fire assay are that the assay fluxes usually contain gold and silver in the lead component of the flux. It is necessary to carry out a blank firing with no ore present to establish how much gold and silver is present in a weighed sample of the flux.

This quantity is then taken off the gold and silver bead from an assay with ore present using the same flux weight.

There will be also some silver present in the bead from the ore, this requires the beads from both the blank and the assay runs to be parted by flattening the beads with a heavy roller, digesting out the silver with nitric acid and weighing the gold residues.

You can see why most assays have an instrumental finish where the entire bead is digested in aqua regia and the amount of precious metals is calculated from the AAS or ICP values.

Most people who sell fire assay equipment tend to gloss over the possible problems or they have done their own fire assays for so long that they really believe that the process is simple, forgetting the amount of learning they had to do.

In your case you have roasted the sulfides so the ore is effectively an oxide ore. You should not be using a sulfide flux on this roasted material.

Never do a magnetic separation on the cons whether roasted or not.

You are almost guaranteeing loss of gold in the magnetics, depending on the conditions of the roast you will generally turn the sulfides into an iron form which will respond to a magnet.

When you are cupelling the lead button you can tell the end point of the cupellation by the button giving a flash of light, this is called the blink.

Before the blink you have a bead which appears to be moving on the surface, after the blink the surface is still.

The more flux you use the more lead you have to adsorb in the cupel, use only the amount recommended for the cupel size you are using.

The main question I have is why you are wanting to do assays on the cons.

If it is for grade and recovery control then you will need an analytical balance which is fairly pricey.

Along with this you will need a lot of experience in doing fire assays.

If all that you want to do is reassure yourself that there is similar levels of gold present then a cheapish microscope will allow you to compare bead sizes without going through the full bead parting and weighing process.

It all comes back to what the mining industry does.

Pretty much all on site assays are done by aqua regia digest and AAS finish.

The results from this procedure are repeatable and the system is generally set up so that unskilled people can do it all after instruction.

You can get a good second hand AAS for the same price as an analytical balance.

Large smelters will usually accept 6oz cons because they can blend them with other higher sulfide feeds and maintain a reasonably consistent feed. You get paid on the fire assay done by the smelter, usually a sample is retained fur umpire analysis in case of arguments. 

If you are wanting to do your own large scale smelting of your cons the simple advice is to forget it.

Your biggest problems are the cost of setting up a smelter and the containment of emissions.

Learning how to run it is hard enough but is easy compared with the other problems.

Deano


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## 4metals (Nov 4, 2015)

Bump!!!!

I really enjoy threads like this and do my best to encourage them, they provide a very sound foundation to the learning process. I hope this thread continues.

Some very good technical information has been made available here. A perfect opportunity for JimiJoe to actually determine the value of his ore, but that requires his participation with more input about the material. I hope this doesn't turn out to be one of those threads that dies because the OP doesn't follow through!


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## Aristo (Nov 4, 2015)

Thanks Deano, great stuff.
One can explain something so easily only because they know it so well.


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## Jimijoe (Nov 5, 2015)

Well Deano, that was a lot to digest. I always send my assays to American Assay because I'm not an assayier. The one vien I'm on Assaed at 6oz. Per ton. The other vien I'm on Assaed at 11oz pet ton. My goal is to just crush the rocks and than table the cons and smelt it. I have been using a RP-4 table, but now I bought a MSI 255 table like on the Gold rush show, I just learned that you have to run different mesh sizes on the table, you just can't take the cons from the roughing table and put it on the MSI table. I'm hoping I can use gravity separation for my small operation. Deano mentioned not to take a magnet to the cons, why is that? Please explane. My last run I had 19lbs of cons off my table #1. I than roasted it and than ran a magnet thru it. I was left with 5 1/2 lbs. of cons. I did save the roasted cons that stuck to my magnet just in case there is gold in there. At the end of the day, I just want to smelt my own cons. This shouldn't be rocket science, but it's so much harder than one would think.


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## Deano (Nov 6, 2015)

Human nature being what it is, there is a great difficulty in sampling a vein to get a representative sample for assay.

The temptation is always to cherry pick the better looking pieces and reject the not so good looking pieces.

Unfortunately if you mine the vein you will have to mine all of the vein material plus any country rock required to give you working room in the drive.

If you are doing it all by small scale hand mining then you can hand sort the mined ore to give you an upgraded semi concentrate.

Whether you are going to use the run of mine ore or the hand picked semi con you will have to mill it to release the sulfides.

This is one area where it will be much better and easier to have someone who has done similar tests to carry out milling of small parcels of ore, say around 0.5 to 1 kg at a time to see what grind size you need to mill to to liberate the sulfides.

The degree of sulfide liberation is determined by doing a float on the milled product and comparing the quantities of sulfides recovered for each grind size.

It shouldn't matter whether you have a friend or a commercial lab carry out this testing but it really has to be done.

You make the small parcels of ore by putting a larger quantity, say 20 kg of run of mine ore, through a jaw crusher to get a minus 6mm or minus 10mm product, depends on what the crusher can get it down to.

The crushed material is thoroughly mixed and then the smaller samples are split out for the testing.

The above will only give you the milling size you have to aim for but it will also allow you to assay the products to see where the gold actually is in the ore.

6 oz ore is rich and rare, what you need to know is where in the ore is the gold.

If it is just in the quartz then you have a different processing route than if the gold is either just in the sulfides or in a mix of quartz and sulfides.

It would be unusual to have 6 oz ore where the gold was just in the quartz and not showing as large pieces but I have seen this occur.

Assuming that the gold is in the sulfides and you can recover the sulfides by tabling (this is why you have to do the above tests) you then have to find out how you have to run the table to get the best recovery of sulfides.

This starts with the rougher table, depending on the grind size required in the mill you will run hundreds of kilos per hour over the table for a coarse grind on a full size table to tens of kilos per hour for a fine grind on the same table.

No matter what table you use it is vital that you have the correct grind size and tabling rate.

If you have lost values on the rougher table you are not magically going to get them back on the clean up table, those values are now in your tailings dam.

Depending on the type of magnet used some sulfides will be attracted to a magnet, this attraction will be fairly weak but still apparent.

It is worth testing to see if your sulfides as is after milling can be separated magnetically with a high strength magnet.

Depending on the type of sulfides you have and how you roast them there is a good chance that you will turn non-magnetic sulfides into magnetic roasted oxides.

If you carry out a magnetic separation on the roasted material you will remove material which is carrying the gold originally in the sulfides.

Get fire assays done on the magnetic cons and tails to see where the gold is.

I am not trying to tapdance around the processing but when all of the answers relate to unknown material I can only give you general directions.


Deano


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## Jimijoe (Nov 6, 2015)

As far as digging the vein goes, I hired a Geologist to go in the mine I'm working in. He pointed out where to dig on the vein, he also did some sampling while he was there. Being a beginner I didn't want to make a lot of costly mistakes. So at that point we dug this vein for 2days, I took that material and crushed it, than thru the impact mill and on to the table, I understand what your saying about the different sizes on the milling. I'm not sure how to do that when I can't adjust my impact mill to different sizes. I understand screening the different mesh sizes for the table. I was told that I should screen 20/30/50/100 mesh and process them separately on my table. I just bought a used MSI table and it's very hard to operate. So I'm going to start screening my cons. Than back to trying to smelt.


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## j2000 (Dec 10, 2015)

Jimijoe said:


> As far as digging the vein goes, I hired a Geologist to go in the mine I'm working in. He pointed out where to dig on the vein, he also did some sampling while he was there. Being a beginner I didn't want to make a lot of costly mistakes. So at that point we dug this vein for 2days, I took that material and crushed it, than thru the impact mill and on to the table, I understand what your saying about the different sizes on the milling. I'm not sure how to do that when I can't adjust my impact mill to different sizes. I understand screening the different mesh sizes for the table. I was told that I should screen 20/30/50/100 mesh and process them separately on my table. I just bought a used MSI table and it's very hard to operate. So I'm going to start screening my cons. Than back to trying to smelt.



Thanks for the story....
So any news now jimijoe?

Joel


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## Cody Reeder (Dec 15, 2015)

Jimijoe said:


> So I pick up all the pieces and put it back in a new kepel and put it back in the oven, waited a half hour, took it out and no button, just scrap from the broken kepel. So I'm confused about where my Gold is at.



Remember those pieces of cupel that were left after the lead disappeared, did you have a good look at them? Ive had bits get stuck to those and mess up my assay before.


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## solarsmith (Dec 27, 2015)

a pin head bead? good job sounds like you did it just right. now dvide the size of your sample into 1000000 grams. and multiply this by the weight of the pin head.
you will know the expected grams per ton 2.200 lbs this is the total pgms in the bead. you will need to do one more step to remove the silver from the bead then weight whats left and you now know the gold content. this is basic assay for gold/silver. when you get your ore to be over 20 oz a ton of gold your ready to do a direct smelt! Bryan


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## Sk8rguy (Jun 26, 2019)

i know its an old post but did you glaze your cupel seems might be a porous issue since you said it broke maybe it soaked up the gold and now you'd have to crush the cupel down and process it to get this bead you saw the 1st time.


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