# recoveryng gold from polishing dust



## asustin (Mar 14, 2012)

which is the best procces to recover gold from polishing dust from jewelry?


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## martyn111 (Mar 15, 2012)

Obviously during the 17 minutes from registering on the forum and asking your first question you didn't do alot of reading. This subject has very recently been discussed.
Try this link but do not expect to get your hand held in the future, we don't work that way here.
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=49&t=13182&p=134114&hilit=polishing#p134114
Then you should search out a copy of Hoke's book, available as a free download from many members signature lines.

Edited spelling and grammar


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## gurudatta (Mar 15, 2012)

hi,
first u must know the greater contents such as silver ,gold,platinum or paladium in your dust.according to this u consider the process.if your dust contains silver metals then you treat it with nitric acid first,then with aqua regia.for other metals aqua regia mehod is suitable .after aqua regia you carry cyanide process for silver and few quanity of gold recvery .


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## nickvc (Mar 15, 2012)

Can I point out that the use of cyanide after any acid process isn't one for hobbyists or amateur refiners and even more so without good extraction. Gurudatta may have a language barrier and I might be reading his meaning wrongly so I'm not trying to jump all over him just point out this could be a deadly procedure and should not be attempted by any but the most experienced professional.


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## Harold_V (Mar 15, 2012)

*What Nick said.* 

We do not promote the use of cyanide on this forum. It is, generally, beyond the capability of the home refiner, and is extremely lethal to handle when not handled properly. 

It takes very little cyanide to kill. Making a transition from acid treatment to cyanide treatment would be more than enough to do so. 

*gurudatta *
I take a very dim view of folks who use text messaging in posting. Please lose the use of *u* for you, as well as any other shortcuts that you may have in mind. Spell in clear, concise English to the best of your ability. Do not use shortcuts. 

Harold


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## asustin (Mar 16, 2012)

Hi everybody! thanks for yours comments. Let me tell you what I did since yesterday. first I burn one pound of jewelry dust that reduced the pound to 260 grams, then I added nitric acid, then I take out the acid to recover the silver later. today I added aqua regia and I'm waiting for tomorrow. What do you think about that?


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## nickvc (Mar 16, 2012)

With polishing wastes heat will be needed to get a decent extraction of values, stirring is also advised on a regular basis especially as the solution heats up to avoid breaking the glass, Harold used to bring his sweeps to a low boil with a watch glass on the beaker to agitate the solution and the powder to achieve a better extraction. You may find a second treatment will be needed to recover at least 95% of the values in the powder, the first treatment usually recovers approximately 90% of the values.


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## Harold_V (Mar 16, 2012)

asustin said:


> Hi everybody! thanks for yours comments. Let me tell you what I did since yesterday. first I burn one pound of jewelry dust that reduced the pound to 260 grams, then I added nitric acid, then I take out the acid to recover the silver later. today I added aqua regia and I'm waiting for tomorrow. What do you think about that?


I don't think much of the process you used, and there's good reason. Please understand that I refined for manufacturing jewelers almost exclusively, so I have considerable experience, in particular with processing polishing wastes and floor sweeps. 

You are far better served to not use nitric acid for the initial digest. In its place, use HCl, and boil the material (covered with a watch glass) for some time. Do not allow the vessel to sit idle while being heated. Stir regularly, so no hot spots develop. Should you heat too long without stirring, when you do, you'll disrupt the superheated layer, resulting in a broken vessel from thermal shock.

The reason to use HCl instead of nitric is because of the problems you'll encounter filtering the recovered gold. The solution often refuses to filter, even with vacuum assist. By washing with HCl and rinsing well, that won't be the case. The only real negative aspect is that you leave behind the silver, but it is not lost. It can be recovered by other means, including fire reduction or cyanide. Even if you lose the silver, assuming that the values come from the bench of a goldsmith, not a silversmith, the losses will be minimal. A small price to pay for the ease of filtration in my estimation.

Harold


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## asustin (Mar 16, 2012)

Hi, thanks for your valuable information, will apply for the next occasion. Let me tell you the procedure I am carrying out. Today in the morning I filtered the aqua regia solution and I know there's a bit of platinum, so I added ammonium chloride to precipitate it. In the afternoon I filtered again and I recovered de sediments that I guess is platinum, and just now I'm going to add ferrous sulfate to precipitate the gold. Thanks for yours comments I really appreciate it.


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## Harold_V (Mar 17, 2012)

asustin said:


> Hi, thanks for your valuable information, will apply for the next occasion. Let me tell you the procedure I am carrying out. Today in the morning I filtered the aqua regia solution and I know there's a bit of platinum, so I added ammonium chloride to precipitate it. In the afternoon I filtered again and I recovered de sediments that I guess is platinum, and just now I'm going to add ferrous sulfate to precipitate the gold. Thanks for yours comments I really appreciate it.


Sounds like you had good fortune in filtering, so you did just fine. 

A little tip that might be useful for you. 

Washing the recovered platinum is not easy, as it will readily dissolve. Instead of recovering traces of platinum before recovering your gold, do the reverse. Precipitate gold first, which can be washed without issue, then precipitate the platinum. In the long haul, from the perspective of the guy with very little platinum, that will make more sense. 

Harold


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## asustin (Mar 17, 2012)

Hi, thank you for yours comments, and let me tell you I had no fortune because to filter 700 ml. I take 3 hours, drop by drop. But now it happens that, gold is not precipitate. so I don't know what to do, the only thing I can think of, is to add more precipitant, but I have no more ferrous sulfate so I'm going to add sodium bisulfite. Thank you very much to this forum, I use a lot of support.


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## butcher (Mar 17, 2012)

Cementing on copper at this point, rinse and incinerate powders, a good boil in HCl and rinses, dilute hydroxide wash heated, rinse and then re-incinerate and start over, would be my choice, I think you have something in this that is just going to keep giving you trouble till you clean it up,


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## Harold_V (Mar 18, 2012)

butcher said:


> Cementing on copper at this point, rinse and incinerate powders, a good boil in HCl and rinses, dilute hydroxide wash heated, rinse and then re-incinerate and start over, would be my choice, I think you have something in this that is just going to keep giving you trouble till you clean it up,


That's part of the reason I suggested the preliminary wash in HCl instead of nitric. I used that method for years and NEVER had any issues with purity or with filtration. If the resulting dirt (from polishing wastes) is given a hard, prolonged boil, the resulting gold chloride solution is a very nice yellow color, without signs of copper or other base metals. I fully expect that's because of the incineration and finely divided nature of the material, where most of the base metal is oxidized and readily dissolved in HCl. As I said previously, the only real negative aspect is that silver is not recovered, although it's also not lost---it's still in the material, now as silver chloride. 

Harold


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## e4me5758 (Sep 25, 2016)

I had gold solution in glass jar muritic an nitric the slution got spilled on the ground.I got all the dirt that was comtamated an then some . Can this be done the same way as the polish dust. Thank you e4me5758


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## 4metals (Sep 26, 2016)

I would first try to give it a hot water soak and filter the water to separate the gold chloride solution from the dirt. Try a small sample and test the filtrate with stannous. A lot depends on the definition of dirt!


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## e4me5758 (Sep 27, 2016)

first try to give it a hot water soak and filter the water to 
Thank you 4metals. I live in calif the dirt is red clay and sand.. I will try a sample an see what happens.please let me know if this type dirt changes the process. Thanks agine e4me5758


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## 4metals (Sep 27, 2016)

Soils with a lot of organics, like loam or mulch, would soak up a lot of the values and you could quite possibly lose them when incinerating the organics as gold salts can volatilize if incinerated at too high a temperature. 

Sand and clay is probably the best dirt you could hope for because you will not have to incinerate it and you may be lucky enough to be able to leach out the values with water rinses.


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