# Gold refining



## tullo (Dec 19, 2017)

hello everybody ,
so i am jeweler and when it comes that time of year cleaning the mess (powder,dust)that i have been working all the time of the polish machine always been interested how do they refine it into pure gold , some of the videos that i watched didn't match the target that i wanted , either they got videos with "Refining gold from karat scrap" or pc parts . can someone tell me step by step how it is made that kind of process with the mess(powder,dust)of the polish machine . peace


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## Shark (Dec 19, 2017)

There is much information on refining jewelers waste, here is one from the forum to get you started.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=52&t=26384#p279924

Hope it helps.


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## FrugalRefiner (Dec 19, 2017)

The book in my signature line was written for jewelers who wanted to refine their own waste. I think it will help.

I deleted your other two posts. In the future, please post your questions only once.

Dave


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## tullo (Dec 21, 2017)

FrugalRefiner said:


> The book in my signature line was written for jewelers who wanted to refine their own waste. I think it will help.
> 
> I deleted your other two posts. In the future, please post your questions only once.
> 
> Dave


i understand , sorry


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## tullo (Dec 21, 2017)

Shark said:


> There is much information on refining jewelers waste, here is one from the forum to get you started.
> 
> http://goldrefiningforum.com/phpBB3/viewtopic.php?f=52&t=26384#p279924
> 
> Hope it helps.


thank you


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## Topher_osAUrus (Dec 21, 2017)

If its just a once a year type deal, it may be in your best interest to find someone to do it for you. That depends on a lot of things though.

-the space you can dedicate to refining
--the ventilation system you put in place for said space
-the volume you are doing
-the number of lots per year
-cost of chems and equipment
-time spent on educating yourself, "labor" essentially

And a lot of other things im forgetting.
Im sure as a jeweler you already have a small torch and cruciblea and some other required stuff

I do small lots for a local jeweler every few months, and the only reason he said he wouldnt do it himself in house was because of the corrosive fumes. If you get a fume hood, and a segregated space for chems and waste, it makes sense to process the stuff yourself.

Cost vs benefit
Beside myself, there are other members(who may live closer to you) that do toll refining.


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## Jordan1 (Feb 18, 2018)

I have recently started refining gold through inquartation and seperation process using acids and aqua regia. I can only achieve 98 % purity though. 

Can someone please give me their advice on refining gold to 99.99% ?

What do you think about the Miller process and electrolytic refining?


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## g_axelsson (Feb 18, 2018)

Jordan1, how do you know it's only 98% pure?

Inquartion followed by aqua regia and precipitation with SMB or copperas followed by proper washing should normally get you closer to 99.95% if done properly.

What is the contamination?

Give us more details or we won't be able to help you.

Göran


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## goldsilverpro (Feb 21, 2018)

Jordan1 said:


> I have recently started refining gold through inquartation and seperation process using acids and aqua regia. I can only achieve 98 % purity though.
> 
> Can someone please give me their advice on refining gold to 99.99% ?
> 
> What do you think about the Miller process and electrolytic refining?



Why do you want 99.99%? With inquartation and then aqua regia, you should easily get 99.95%, if you do things right.


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## Jordan1 (Feb 22, 2018)

g_axelsson said:


> Jordan1, how do you know it's only 98% pure?
> 
> Inquartion followed by aqua regia and precipitation with SMB or copperas followed by proper washing should normally get you closer to 99.95% if done properly.
> 
> ...



Hi there,
I had a friend of mine checked it with a xrf gun. 98.02% purity

It was dissolved into aqua regia and precipitated with copperas.

The rest of the contaminent is silver.


Thanks,
Jordan


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## Shark (Feb 22, 2018)

Others may have a better idea but in my case when silver is the major contaminant it is usually related to poor filtering. Once I reached a point where I examined my filters a bit more thoroughly and made changes accordingly I found my quality made a serious improvement.


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## anachronism (Feb 22, 2018)

Spot on Shark you nailed it. 

The filtered liquid needs to be crystal clear to reduce the silver contamination. You need to be able to read a newspaper clearly through the liquid.


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## goldsilverpro (Feb 22, 2018)

Silver is fairly soluble in strong aqua regia but nearly insoluble in weak aqua regia.Therefore, let's say you filter the strong aqua regia and get it crystal clear. Then you rinse the filter. This dilutes the AR a little and more silver precipitates, putting you back to square one.

There are only 2 ways I know of to drop out most of this dissolved silver, so it can be filtered out. My favorite way is to simply dilute the AR solution with 3 parts of tap water per part of AR. This will precipitate about 98% of the silver. The other method is to chill the AR solution with a lot of ice. The problem I always had with the ice was to get the solution filtered before the solution warmed up and redissolved some of the silver chloride. I strongly believe that more silver can be removed with dilution than with ice and it works every time.


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## snoman701 (Feb 22, 2018)

GSP's post is spot on.

I have been diluting my AR with ice...by the time all of the ice melts and it makes it through the filter, it's usually at 20 deg C. My AR can then be crystal clear...you can not only read the newspaper, but if you hit it in the right spot, it magnifies the pictures and you can see the dots. 

After precipitation of gold, I don't wash with HCl...just rinse with distilled water quickly. (I only get paid to two decimal points, so why bother?)

On wavelength dispersive XRF, this gold still comes out at .992-.997, with the only contaminant being Ag.


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## Shark (Feb 22, 2018)

I agree with GSP also. I forget sometimes that others use different methods but I have followed GSP's way for quiet sometime now. By using the dilution method I cured many of the problems I had when using ice. Those remaining problems are where the filtering made the major improvements for me. One day I need to get some testing done to see where the purity stands, but that is just for my curiosity.


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## anachronism (Feb 23, 2018)

How do you define strong AR vs weak AR Chris? Do you mean heavily pregnant vs less?


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## autumnwillow (Feb 23, 2018)

anachronism said:


> How do you define strong AR vs weak AR Chris? Do you mean heavily pregnant vs less?



I think weak AR is diluted AR. The problem with using weak AR is that the digestion will be very slow but it will lower the chances of your gold chloride turning into a vapor. A strong AR will definitely put gold in your scrubber system even without heating. I observed this when I checked my condenser tube liquid with stannous.

Ag contaminant can be avoided by following GSP's advice but remember to use a #5 or #42 filter paper. Coffee filters are not up to the job. I used a #2 filter paper before and had poor results.

Edit to add: depending on where you are from. I wouldn't use tap water just to be sure.


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## nickvc (Feb 23, 2018)

The only problem is the amount of waste solution you create which for some becomes a major headache, if the gold is going back into jewellery manufacture the small amount of silver makes very little to no difference so long as you know the actual purity so it isn’t worth the extra waste solution. 
You could try filtering the solution twice through the same filter paper preferably using a vacuum pump, as the filter slowly clogs it catches more and more small particles or even add ice to the filter to drop the silver chloride and catch it in the paper.


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## goldsilverpro (Feb 23, 2018)

anachronism said:


> How do you define strong AR vs weak AR Chris? Do you mean heavily pregnant vs less?


I should have worded that differently.

By strong AR, I meant undiluted AR. By weak, I meant after diluting 3 to 1 with water. I should have said that the greater the amount of dilution, within limits, the less the solubility of AgCl. About 50 years ago, I did a set of experiments. It's been a very long time but this is how I remember it. I don't remember if I also had gold dissolved in the AR, but, to duplicate karat gold processing, I probably did add Au, along with some copper. I started with undiluted AR that was saturated with AgCl at room temp and the dissolved Ag was analyzed by AA. I then diluted it 1 to 1, filtered it until crystal clear with glass fiber paper and then analyzed the silver by AA. I then repeated this with 2 to 1, 3 to 1, 4 to 1, and 5 to 1 dilutions. I found that the 1 to 1 dilution eliminated about 50% of the Ag, if I remember right. The 2 to 1 removed a large proportion of what was left. The 3 to 1 reduced the Ag to near zero and, beyond that, the curve flattened out and there was little or no improvement. Therefore, I included 3 to 1 dilution in my production process and have never had a reason to change it.

I can't remember a person's name but, for some strange reason, I can usually visualize and remember most everything I have done with PMs in detail, no matter how long it's been. Most of the time, I can even remember yields.


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## anachronism (Feb 23, 2018)

Thanks for the clarity Chris.

Nick alluded to a point that I wanted to expand upon. If you have a situation where you've processed lots of processors in AR and you have 12 litres of solution that's loaded with in excess of 13g of gold per litre, and all the associated base metals including silver:

Would you still create an additional 36 litres of waste to get the silver out on the first pass or would you filter and drop immediately. Then redissolve in a much smaller volume say under a litre and subsequently triple the volume of this much smaller amount in order to get clear of silver?

Nick, Pat, and I have done it on the basis of using the first (larger volume) dissolve as recovery, and the second (small volume) dissolve as refine on many occasions and find it to generate much much less waste overall. 

I understand that if it's initially small quantities of gold and liquid then it doesn't make much of a difference but I'd appreciate your thoughts. 

Jon


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## goldsilverpro (Feb 23, 2018)

anachronism said:


> Thanks for the clarity Chris.
> 
> Nick alluded to a point that I wanted to expand upon. If you have a situation where you've processed lots of processors in AR and you have 12 litres of solution that's loaded with in excess of 13g of gold per litre, and all the associated base metals including silver:
> 
> ...


In that case, I wouldn't dilute the 1st drop 3 to 1. I always like some dilution to make the gold drop go smoother, especially with all those dissolved base metals, and would probably do a 1 to 1 dilution for the first drop. Then I would redissolve the Au and do a 3 to 1 for the 2nd Au drop. Every deal is different. 

For karat gold, I don't inquart unless I have green gold or maybe some left over solids from a previous batch. I just dissolve in very hot AR and then use a 3 to 1 dilution. This dilution reduces the effects of too much nitric, to a limit, and also eliminates most all of the effect on Au purity from all those dissolved base metals. I rarely need a 2nd refining and I never need to get rid of excess nitric with karat golds. I did have a method of cleaning up slightly off-purity gold in the melt by using a few pinches of niter, borax, and soda ash. That almost always worked. To me, though, the main secret of good salable purity is in the dilution and crystal-clear filtering. 

If the Karat gold items aren't bulky, I don't even shot them. When the dissolving gets too slow, I use one of several methods to get rid of the AgCl crust. I'm a play-it-by-ear refiner, especially with karat gold, and I've always said that I have never done karat gold the same way twice. That's an exaggeration but not much of one. However, I've never worked in a refinery where karat golds were the main item. If I did, I would develop the ideal method, like 4metals does, and get the right equipment to handle it. Except for the film refinery I worked in, all the rest were job-shop refineries, i.e., they took in anything that would make money, even scrap base metals occasionally. Most of them, including the 2 I had, always had a batch of karat gold cooking away in the back corner of the hood. My little karat gold batches usually held only 5-10 oz of gold.


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## g_axelsson (Feb 23, 2018)

When I do CPU:s in AR I use too little AR to run it to completion in the first time. When the reaction dies down I test the liquid and if it is barren (often is) I pour off the waste into a settling beaker, cover the CPU:s with AR again and continue dissolving metal.
If I time it right I can remove most of the base metals before the final run when I put the gold into solution. This gives me a concentrated solution with a high gold content and not too much base metals. The gold usually drops very nicely.

Any gold dissolved in the beginning cements back onto the exposed metal. First run is always with a smaller amount of nitric, just enough to pierce the plating so the acid gets full access to the base metal underneath. By having a lot of HCl in the first run it's the perfect way to expose the kovar pins and then dissolve them in HCl without wasting a lot of nitric acid.

My method (which I first read about here on the forum) suits me well but it takes longer time, especially since I don't use heating. The solution sits in a safe place outside and I check on it daily.

Just as Chris I'm judging what to do based on what happens while I'm refining. Every batch is different... or at least behaves differently.

If Dave is a frugal refiner, I am a slow refiner. :lol: 

Göran


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## FrugalRefiner (Feb 23, 2018)

g_axelsson said:


> If Dave is a frugal refiner, I am a slow refiner. :lol:


Sounds like a frugal approach to me! 8) 

Dave


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## anachronism (Feb 23, 2018)

FrugalRefiner said:


> g_axelsson said:
> 
> 
> > If Dave is a frugal refiner, I am a slow refiner. :lol:
> ...



If I even UTTER the word frugal to my other half, her eyes turn to chips of stone... Then again she works darned hard for her money so let her enjoy it. 8)


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## goldsilverpro (Feb 24, 2018)

g_axelsson said:


> When I do CPU:s in AR I use too little AR to run it to completion in the first time. When the reaction dies down I test the liquid and if it is barren (often is) I pour off the waste into a settling beaker, cover the CPU:s with AR again and continue dissolving metal.
> If I time it right I can remove most of the base metals before the final run when I put the gold into solution. This gives me a concentrated solution with a high gold content and not too much base metals. The gold usually drops very nicely.
> 
> Any gold dissolved in the beginning cements back onto the exposed metal. First run is always with a smaller amount of nitric, just enough to pierce the plating so the acid gets full access to the base metal underneath. By having a lot of HCl in the first run it's the perfect way to expose the kovar pins and then dissolve them in HCl without wasting a lot of nitric acid.
> ...


I think I was the one to originally post the method, about 9 or 10 years ago. The first time I saw that done was nearly 40 years ago. The guy had a steam heated 50 gallon Pfaudler kettle about 1/2 filled with stainless and inconel parts that were gold brazed. A lot of the extraneous non-gold-bearing base metal had been sheared off before dissolving. He dissolved the base metals with AR (he added the HCl and HNO3, separately, as needed - a gallon of AR will dissolve about 2 pounds of most common base metals) to the point where the AA showed dissolved gold. At that point, I doubt if there was more than 1-2% of the base metals left undissolved. He then cut the heat and added some additional base metals to cement the dissolved gold until the AA showed no gold. At that point, everything was stopped. After settling, siphoning, and filtering, the solids were transferred to beakers and dissolved in AR. The gold was then dropped, as normal. Very impressive. Since then, I've used the process for various types of High base metal material. Works great.

As an experiment, several times I have split a lot of material just to see if the 2 halves reacted the same throughout the process They never did. There was always something that necessitated doing something different to one of the halves.


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## anachronism (Feb 24, 2018)

It's funny how these things come about isn't it? I do something similar 8) I must admit I hadn't wanted to bring it up before now in case I was actually doing something dumb.


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## goldsilverpro (Feb 25, 2018)

anachronism said:


> It's funny how these things come about isn't it? I do something similar 8) I must admit I hadn't wanted to bring it up before now in case I was actually doing something dumb.


As long as a process is safe, efficient, fast, simple, cheap, low labor, and fun, basically in that order, nothing you can ever do is dumb. I would say that safe and efficient are nearly tied for first. By efficient, I mean that you're getting all of the values or, at least all but that last little bit which is too expensive to worry about.


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## deandadnaed (Mar 11, 2018)

Ok guys. I’m a newbe. So please be patient with me.

The first times I did this:

Adjust pH to 12 using NaOH in solution (when I do this the adjustment always produced Ammonia).
I use 2g of Zinc powder (.325 mesh) for every 1g of Gold that I know is in the solution. I know 2NaAu(CN)2+ Zn > Na2Zn(CN)4 + 2Au. I add the Zn while stirring.

I let the solution settle over night.

Then I filter the solution. The liquid contains cyanide so I add either H2O2 or Sodium Hypochlorite to oxidate CN. The solids are dried and transfered to a beaker. I cover them with water and I use HNO3 (under a fume hood). Gas evolves and I continue adding HNO3 until no reaction is observed.

I filter the solids, neutralize the liquid with Sodium Carbonate. The solids are washed and heated in dilute HNO3. When no more reaction is observed. I filter again, neutralize the liquid. And the solids are a dark brown powder.

But my actual yield is very low.

Can anybody give me some advise?

I cannot denox the main solution because it contains Cyanide, so adding Sulphuric Acid or Hydrochloric Acid is out of the question.
I cannot use FeSO4 because it does not precipitate gold in alcaline solutions.
I wonder if NOx are preventing to precipitate all gold in the solution, but I’ve tried adding Zinc in excess to “force” the equilibrium and precipitate gold but it hasn’t improved and naturally I use more HNO3 to leach it and leads to more NO2 formation which is very nasty.

I wonder also if Ammonia has any relation to the low yield. And how can I get rid of the Ammonia (that by itself is very unpleasant to work with).

Please, help. I’m stucked with this problem. I’m willing to do this right and to learn from those who are more experienced.

Any help will be appreciated. Thank you in advance.


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## anachronism (Mar 11, 2018)

If you are trying to get the gold out, I would question why you are adding an oxidant to the solution as part of the process. What purpose does it serve?


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## deandadnaed (Mar 11, 2018)

Hi!

I don’t get it.

If you’re talking about Peroxide/Hypochlorite. I add it to destroy the remaining CN once I’ve filtered the (Zn+Au). 
If you mean HNO3, I use it to dissolve the Zn, and let the Au stay.

But I’m still learning. I’m open to ideas/advises.

Thanks for reading me!


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## deandadnaed (Mar 11, 2018)

When I do the addition of Zinc. I let the solution stay and settle.

I decantate:

To the liquid (which I believe has some CN) I treat it with Peroxide or Hypoclhorite. 
The solid is dried and transfered to a beaker and I add HNO3 to leach out the Zn (though it has some ZnCN). So I’m aware I still got a lot to learn, but that’s why I’m trying to get advise in order to: make things safely, and improve the quality and yield of my work.


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## nickvc (Mar 11, 2018)

How do you know your yield is low, do you know how much is in the solution and if so how?
You may find that to recover the gold you will need an excess of zinc dust, also heating the solution helps but add the zinc slowly to avoid a boil over, adding a little caustic to the solution I also find helps. The other alternative you have is to plate the gold out of the solution which will avoid a lot of the nasty fumes and dangers of mixing cyanide and acids, you will not recover all the gold but if done correctly most of it leaving what’s left for zincing.


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## deandadnaed (Mar 11, 2018)

nickvc said:


> How do you know your yield is low, do you know how much is in the solution and if so how?
> You may find that to recover the gold you will need an excess of zinc dust, also heating the solution helps but add the zinc slowly to avoid a boil over, adding a little caustic to the solution I also find helps. The other alternative you have is to plate the gold out of the solution which will avoid a lot of the nasty fumes and dangers of mixing cyanide and acids, you will not recover all the gold but if done correctly most of it leaving what’s left for zincing.


Thank you very much for your advise! I really appreciate it.
I indeed know how much gold is diluted in AR. So I know how much is in solution. These are my first attempts in recovery. Perhaps I’ll get better when I practice until I master the technique.

Still I wonder if someone has attempted to work in such a system. Hoke’s right, best way to go is by FeSO4, or SMB. But my problem is, I don’t have Au from AR only, in that case it’s a little more straight the methods with less hazard involved. But I’m bounded by cyanide to high pH values. 

I was wondering, if I destroy Cyanide with the Au in it (by Peroxide or Hypochlorite) can I destroy NaAu(CN)2? In that case does anyone think I’d be left with AuCl3 (for the Hypochlorite, for Peroxide I’d be adding some HCl once the Cyanide is gone) and then proceed via Hoke’s (denox, copperas or smb and so on)?

So basically I can’t follow Hoke’s because in spite of being gold dissolved in AR it contains also Ammonia and Cyanide.
I follow something like Merril-Crowe (Gold cementation by Zinc additions) I’ve read the method posted in this forum by goldsilverpro, and yes, it works. I just don’t know if that methods is the best when Ammonia, Citric Acid, and presumably an excess of NItric in AR. Because it’s not Sodium Gold Cyanide salt that has been dissolved in water, but Gold attacked in AR (forming AuCl3) which is later added Ammonia, Citric Acid and the cyanidated (by adding NaCN). I know Sodium Gold Cyanide is the same either prepared from metal or from salt. But my solution contains also Ammonia, Citric Acid, and I consider an excess of Nitric (just to be sure).

:shock:


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## anachronism (Mar 11, 2018)

deandadnaed said:


> I don’t get it.
> 
> If you’re talking about Peroxide/Hypochlorite. I add it to destroy the remaining CN once I’ve filtered the (Zn+Au).
> If you mean HNO3, I use it to dissolve the Zn, and let the Au stay.



Peroxide is most commonly used as an oxidant for the CN whilst Hyopchlorite can be used to destroy CN. If you're adding peroxide you can re-dissolve your gold and make your solution active again which will cause problems dropping the remaining gold.


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## deandadnaed (Mar 11, 2018)

anachronism said:


> deandadnaed said:
> 
> 
> > I don’t get it.
> ...



You’re absolutely right!
By adding and oxidizing agent I’m at risk to oxidate Au itself affecting the reduction to metal state. I’m not sure when the equivalent point of CN with H2O2 is, so I always add an excess just to be sure. But that is done to the liquor that I obtain after the Zn addition. At this point I don’t expect the liquor to have but small amounts of Gold. The solids I’ve filtered is where the Gold metal, and Zinc metal (that has neither been used in displacement nor in the hydroxide formation ZnOH because it’s done at pH=12) should be.

If I understand correctly that grey powder which contains Au and Zn both in metal states, that I can treat with HNO3 to leach out the Zn. Au being in metal state should neither be redissolved nor attacked. 

But again, that’s textbook chemistry. I know that in actual life things often run differently.

Thank you very much for your counsel.


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## anachronism (Mar 11, 2018)

It's my pleasure. 8) 

Jon


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## deandadnaed (Mar 11, 2018)

Well. 

As newbe I’ve got another cuestion. 
I’ve melted my button. Although the metal has some Borax crust all over the surface. I assume I’ve did a poor job when glazing my crucible.  

Any suggestions on how to get rid of the Borax crust?

Also. Can anybody tell me some tips to improve glazing my crucible in order not to end when I melt my metal with a borax crust?


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## kernels (Mar 11, 2018)

There are a few ways to remove the borax, you can heat the gold button up to red hot again and drop it in some cold water. You can also just put the whole button in a flask and boil it in water for a while, the borax will flake off / dissolve.


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## deandadnaed (Mar 11, 2018)

kernels said:


> There are a few ways to remove the borax, you can heat the gold button up to red hot again and drop it in some cold water. You can also just put the whole button in a flask and boil it in water for a while, the borax will flake off / dissolve.


Thank you! I really appreciate all the support I’ve been given. This is my first attempt and you must know all the mixed emotions one can bear when you achieve something for the first time.
I thank you all. 


Enviado desde mi iPhone utilizando Tapatalk


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## anachronism (Mar 11, 2018)

You can also put the button in dilute sulphuric acid and warm it. Leave it there and you will see the borax disappear.


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## deandadnaed (Mar 12, 2018)

anachronism said:


> You can also put the button in dilute sulphuric acid and warm it. Leave it there and you will see the borax disappear.


Thank you very much!
I’ll try it! Hopefully I’ll be having less this problem as I develop skills when melting.



Enviado desde mi iPhone utilizando Tapatalk


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## Jordan1 (Mar 20, 2018)

Shark said:


> Others may have a better idea but in my case when silver is the major contaminant it is usually related to poor filtering. Once I reached a point where I examined my filters a bit more thoroughly and made changes accordingly I found my quality made a serious improvement.



Hi Shark,

You are right. I took my time and washed the gold properly with hcl and distilled water and achieved 99.99%.

Parting with nitric and the wash i have found the most important part to getting the purest metal possible.

Thanks


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## goldsilverpro (Mar 20, 2018)

Jordan1 said:


> Shark said:
> 
> 
> > Others may have a better idea but in my case when silver is the major contaminant it is usually related to poor filtering. Once I reached a point where I examined my filters a bit more thoroughly and made changes accordingly I found my quality made a serious improvement.
> ...



I wouldn't trust XRF to guarantee that that purity is correct.


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## Jordan1 (Mar 21, 2018)

goldsilverpro said:



> Jordan1 said:
> 
> 
> > Shark said:
> ...



Why is that goldsilverpro? The metal was tested with 2 xrf machines. 

What would you trust for a accurate assay?


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## anachronism (Mar 21, 2018)

To be honest it depends on who is buying your material as to whether an xrf is accurate enough. 

If your buyer uses one and it says 99.99% then everyone is a winner.


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## FrugalRefiner (Mar 21, 2018)

Jordan1 said:


> Why is that goldsilverpro? The metal was tested with 2 xrf machines.
> 
> What would you trust for a accurate assay?


See Help with XRF results (99.70% Au 0.30% Ni).

Dave


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## modtheworld44 (Mar 23, 2018)

anachronism said:


> To be honest it depends on who is buying your material as to whether an xrf is accurate enough.
> 
> If your buyer uses one and it says 99.99% then everyone is a winner.



anachronism

I agree with you 100%.

My guy buy's gold based on xrf.I tested the accuracy of his gun myself.I took him a 61.2 gram button that I left the top fire scaled.The bottom and sides shot 99.99% and the top shot 99.98%.He told me at that time he would pay 95% of spot,I declined the offer because I was looking for at least 97%.I then went home and centered the button with sodium nitrate and pickled it in dilute nitric,this was done six times across 2 and half hours.The last centering left a brand new crucible with crystal clear borax.The new weight ended up being 61.1grams and was re-shot at 99.99% on all sides of the button and he then payed me 97% of spot and sent 10 lbs of pins home with me to be refined.Thanks in advance.



modtheworld44


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## Lou (Mar 23, 2018)

Looks are everything!!


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## anachronism (Mar 23, 2018)

Lou said:


> Looks are everything!!



That's me screwed then Lou.


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## goldsilverpro (Mar 24, 2018)

Lou said:


> Looks are everything!!


I totally agree with Lou. Experience will tell a knowledgeable person whether a bead, button, or bar is at least 99.95% pure, or not, by just looking at it after it cools. That's why I never keep the torch on the bar, as it cools, to get those concentric circles. I wanted my expert buyer to see the crystal and the pipe. When I had my last refinery, I shipped gold at least once a week, always got paid for pure gold, and never had a lot bounce back, all based on visual appearance, at both ends. I also never shipped any discolored gold that I could have easily made look good. Although rare, any gold with Pt Gp chicken tracks or discoloration or any other visual defect was re-refined. The small bead in the photos above, would be unacceptable and would be re-refined. There's more problems with it than a little slag on it.


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## Jordan1 (Apr 1, 2018)

Hi,

I would like to know if anyone on the forum has processed gold / silver dore bars from the mines ?

I know that the purity varies from mine to mine, though wanted to get a good idea of gold / silver % and other contaminants in the dore bars? 

Thanks


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## Jordan1 (Apr 24, 2018)

goldsilverpro said:


> Jordan1 said:
> 
> 
> > Shark said:
> ...


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## goldsilverpro (Apr 25, 2018)

For high purity gold, ICP. For everything else, fire assay.


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## cuchugold (Apr 26, 2018)

If anyone wishes to make a small experiment: After you have your "clean" aqua regia, and before reduction of the metal, drop a pH strip in the clear liquid, and start dropping a solution of sodium hydroxide till the pH strip is about color 6.5 (near neutral). Wait for the few solids to coalesce and settle, and then decant. Adding a little zinc or barium chloride to the initial solution helps in collecting the solids. This really gets the rest of the silver out, and a few other things too. If it doesn't, I'll refund every penny you paid for the free advice. 

You can start selling the expensive assay equipment soon after. You won't need it anymore. :G

edit: This, in 'first principle' is parallel to GSP's dilution method, but without the extra water. But do not think too hard about it. The experiment is easier to make than the thinking.


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## Deano (Apr 26, 2018)

Dore bars from commercial mines vary dramatically in their contaminant contents, there is no one size fits all.

Silver runs from 1 to 20%, often around 10%

Copper runs from 1 to 30%, sometimes more, very mine ore type dependent.

Iron from electrowin steel wool varies as to the actual method detail of aciding it out before smelting.

Levels of other metals such as lead, nickel and chrome depend on both the ore types and treatment methods, usually in single digit % or less.

Overall purity of the bars can run from 30 to 95% gold, below 30% the penalties really hurt.

Deano


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## 4metals (Apr 27, 2018)

I can understand the refining costs going up for doré gold which is below 30% gold but I am surprised it doesn't go up for higher silver. I worked with an Asian refinery which routinely received doré from a region with the silver content at 23%. Very much a pain to refine! 

I would think silver in excess of 15% should carry a penalty as well, unless they already bang the guy with ridiculous silver refining rates! Then they just deal with it!


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## kuli (Jul 24, 2018)

Hi again,

I put cca 100g of phone board.
After filtering in put SMB. a little bit 10g. 
If you look at solution there is nothing.
Where did i missed?
Help please. I put first SMB to cold water and then drop to solution.

regards


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## anachronism (Jul 24, 2018)

If you used 100g of phone board then the chances of you seeing gold are slim to none.


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## nickvc (Jul 24, 2018)

anachronism said:


> If you used 100g of phone board then the chances of you seeing gold are slim to none.



:roll:


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## g_axelsson (Jul 24, 2018)

kuli said:


> Hi again,
> 
> I put cca 100g of phone board.
> After filtering in put SMB. a little bit 10g.
> ...



As stated by others too, there is very little gold on 100g of phone boards. Most of the gold is just flash plated.
A lot of the gold in cellular phones are hidden inside the circuits in the form of bond wires.

If it was ordinary phones with a cable then there is almost no gold at all in them.

Göran


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## g_axelsson (Jul 24, 2018)

Please do not double post, I have removed your other post.

Göran


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