# Removing stones from scrap jewelry?



## Roxx (Apr 20, 2008)

So I am just getting into the whole karat gold business and ws wondering how one would remove the stones from old broken rings and etc. without scratching or damaging the stone?

thx
-roxx


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## banjags (Apr 20, 2008)

you need to very carefully bend the little fingers holding it down. Depending on the cut of stone the will be 4 or more.


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## Harold_V (Apr 20, 2008)

Roxx said:


> So I am just getting into the whole karat gold business and ws wondering how one would remove the stones from old broken rings and etc. without scratching or damaging the stone?
> 
> thx
> -roxx


I refined for a pawn shop that didn't remove the small stones, anything under about .2 carat in size. I used a flex shaft and a small abrasive disc to cut the prongs. Doing them by other means was too slow, because the amount of scrap submitted for refining was large----often yielding near 100 ounces of gold. I made more money on the removed diamonds than I did on the refining. They didn't want them returned. 

You need not fear hurting a diamond with a grinding wheel of the type I described-----but softer stones can be harmed if you don't use care. For me, it was worth the risk to make stone removal a faster process. 

I made a small glove box with a viewing window (piece of large diameter plastic pipe with a Lucite window) so I could catch the grindings that came from the stone removal process. No losses that way. 

Harold


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## Noxx (Apr 20, 2008)

Why all this trouble ?
I simple dissolve the gold and the diamonds stays at the bottom. You can recover them after filtering.


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## goldsilverpro (Apr 20, 2008)

Some stones won't stand up to the aqua regia. Pearls will definitely be attacked.


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## Roxx (Apr 20, 2008)

Wow great answers abound around here. I agree with Catfish's general idea that personal refining of Karat Gold isn't very lucrative, but if the best way to remove stones is to dissolve the gold around them it may be more economical to do the refining in-house just to recapture the stones.

So I guess I'm saving up for Hoke's book.

Is AR the best method of dissolving karat gold from around stones or would a reverse electrolysis process be better.

-roxx


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## Noxx (Apr 20, 2008)

AR is NOT the best method for karat gold since you have silver alloyed with your gold.

I would recommend karat cell.


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## goldsilverpro (Apr 20, 2008)

After leaching with nitric (if 10K was present), I always used AR directly on most all karat gold. If anything was left over, I would inquart it and get it next time. RARELY was anything left over. Please note, however, that I was buying the karat gold I was processing. It was mine. I owned it. I could process it any way I wanted. I didn't have to get it all the first time, although I usually did. I personally think that direct AR is the best way to run karat gold or dental gold.


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## Noxx (Apr 20, 2008)

I agree that you must use Nitric prior AR. But I wouldn't call it direct Aqua Regia 

GSP, you are using nitric acid with 10k gold and lower I suppose ? What if it is 14k-18k ? And do you use 35%-40% Nitric Acid ?

Thanks


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## goldsilverpro (Apr 20, 2008)

With a mixed lot, 6K through 22K, I always first hit it with hot 50/50 nitric. It may or may not dissolve something. Then I pour it off, cover it with an excess of HCl, heat it up, and feed it with small increments of HNO3. When an addition of HNO3 produces no reaction, I know I'm finished. No urea needed. No evaporation needed. Why? - because I didn't use an excess of nitric. In most cases, all the karat gold is dissolved. If anything is left, I inquart this small amount. There will always be some trapped Au solution in the AgCl. This is easily recovered during the AgCl to Ag conversion.


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## Noxx (Apr 20, 2008)

Alright thanks.


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## Roxx (Apr 20, 2008)

Ok so i think I might be getting the idea behind this. The nitric acid bath will get rid of the silver , and the HCL and HNO3 combination dissolves the gold. At which point i will need a precipitant to recover the pure gold mud. I currently have just 2 questions:
1. Do I need to rinse and dry my material in between the nitric bath and the start of the AR process?

2. How will all these abrasive chemicals effect the quality of the stones 
I wish to retrieve from the solutions? Both Diamonds and semi-precious stones.


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## goldsilverpro (Apr 20, 2008)

(1) No. Just let everything settle and then pour off as much nitric as you can. Then, go to AR.

(2) No problems with diamonds. Some of the other stones can be affected. I don't have a list. Pearls are severely affected.


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## Roxx (Apr 21, 2008)

What about reverse electrolysis? If I built a karat cell would I be able to quickly recover the gold without harming the stones?


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## Palladium (Apr 21, 2008)

The diamonds are made from carbon so they are pretty rugged. Pearls are more of a organic and will be affected by chemicals of high oxidation i.e. Nitric, sulfuric, or any strong oxidizer. Just think of what happens when your skin is exposed, it organic.

Pearls 

Contrary to popular belief, pearls hardly ever result from the intrusion of a grain of sand into an oyster's shell. Instead, a pearl forms when an irritant such as a wayward food particle becomes trapped in the mollusk. The animal senses the object and coats it with layers of aragonite ("ah-RAG-uh-nite") and conchiolin ( "KON-kee-uh-lin"). These two materials are the same substances the animal uses to build its shell.

In most pearls, the mineral aragonite is arranged in sheets of flat, six-sided crystals. Between each sheet, the mollusk secretes a very thin layer of the membrane-forming protein conchiolin. This composite material is called nacre ("NAY-ker") or mother-of-pearl. The crystalline structure of nacre reflects light in a unique way, giving so-called nacreous pearls their high luster. In contrast, some pearls are not nacreous and instead have a low-luster, porcelainlike surface. The needlelike crystals of aragonite in these pearls are arranged perpendicularly or at an angle to the surface of the pearl.


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## browninkie (Jul 11, 2014)

goldsilverpro said:


> With a mixed lot, 6K through 22K, I always first hit it with hot 50/50 nitric. It may or may not dissolve something. Then I pour it off, cover it with an excess of HCl, heat it up, and feed it with small increments of HNO3. When an addition of HNO3 produces no reaction, I know I'm finished. No urea needed. No evaporation needed. Why? - because I didn't use an excess of nitric. In most cases, all the karat gold is dissolved. If anything is left, I inquart this small amount. There will always be some trapped Au solution in the AgCl. This is easily recovered during the AgCl to Ag conversion.



This method seems like it goes against what I've been learning in Hoke's book. 
Without the inquartation process and proper nitric acid digestion, wouldn't the AR digest all the base metals along with the gold..resulting in gold containing lots of contaminants?
And also, doesn't the formation of AgCl prevent the karat gold from dissolving in the first place?
Is there some sort of industrial method of refining gold without inquarting to 6k?

I just finished Hoke's book, so I still have a lot to learn  
Hope you can clarify this~~ thanks in advance!


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## justinhcase (Jul 11, 2014)

I use a small Ammonium and sodium Chloride electrolyte stripping cell. U.S. Patent 4895626.
The hook to hold the ring is made out of Titanium(anode) so is unaffected by the process,and the cathode is stainless steel.
I still only add enough electrolyte to cover the part of the ring that has stones.
I had some white gold rings with nice diamonds left ,the larger ones had been removed before me.,but the settings where to deep to pry out.
So I ran it in the cell for two or three hours,the stones drop out easily and I just put all the filtered cell slime straight into my next Inquartation .
Will work with any alloy and Ammonium and Sodium Chloride will only affect the most vulnerable of stones.


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## nickvc (Jul 11, 2014)

In refining and recovery sometimes we need to achieve slightly different things recovering valuable stones from karat scrap been one example thereof.
The procedure is the same as mine, you boil all the scrap in nitric in the hope it removes some of the base metals and silver if present followed by the AR to dissolve the metal from around the stones, in some cases all the gold will dissolve in others as you noted silver chloride will form a protective shell and stop it but hopefully enough metal dissolves to allow easy stone recovery.
This whole process is really a recovery rather than a refining process.


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## browninkie (Jul 11, 2014)

justinhcase- Thanks for the patent number and new technique. That method seems to be the one that gives the least hassle in removing stones. I think I'll have to do more research on it though. Whenever I read ammonia, I want to make sure it's not going to become a problem with my metals :shock: 



nickvc said:


> This whole process is really a recovery rather than a refining process.


This is what I was leaning towards. Which got me wondering about the process..
1. Leave the jewelry with stones in AR long enough until the stones can be removed. 2. Once stones are gone, clean the gold piece and Inquart and proceed as usual.
If the AR digests the jewelry enough for the stones to fall out, am I correct in thinking that the AR solution will now contain traces of gold along with other base metals? What am I supposed to do with this "contaminated" AR solution? 

I was concerned that if I proceed to precipitating the gold, all the other base metals drop out as well, therefore leaving me with impure and brittle gold..
Or is this "contaminated" AR solution something that goes into the stock pot and recovered later.

Thanks for the replies ^^
Still trying to learn all the methods so I can avoid trouble down the road
Cheers


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## goldsilverpro (Jul 11, 2014)

That's one of the Shor patents.


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## FrugalRefiner (Jul 11, 2014)

browninkie said:


> This is what I was leaning towards. Which got me wondering about the process..
> 1. Leave the jewelry with stones in AR long enough until the stones can be removed. 2. Once stones are gone, clean the gold piece and Inquart and proceed as usual.
> If the AR digests the jewelry enough for the stones to fall out, am I correct in thinking that the AR solution will now contain traces of gold along with other base metals? What am I supposed to do with this "contaminated" AR solution?


You don't necessarily have to pull the items out as soon as the stones are out. Some gold alloys will dissolve completely in AR. The problem alloys are usually those with a silver content over about 8 to 10 percent. If it dissolves, you're fine. If it doesn't, you can dissolve the silver chloride crust with thiosulfate or ammonia (be sure to reacidify the ammonia solution promptly). Then you can inquart any pieces that remain.

Yes, you will probably have both gold and base metals in solution. You precipitate the gold from the dirty solution with a selective reducing agent, knowing there will be a lot of contamination. Wash it properly, then re refine it a second time.



> I was concerned that if I proceed to precipitating the gold, all the other base metals drop out as well, therefore leaving me with impure and brittle gold..


That's why we use the reducing agents we do. They're selective for gold. While there will be some contamination from the dirty solution, done correctly, the majority of the base metals will remain in solution.



> Or is this "contaminated" AR solution something that goes into the stock pot and recovered later.


You add your solution to the stock pot only after you've removed as much of your values as possible.

There's much more to it than my simplified answers indicate, but hopefully they'll point you in the right direction. Keep studying Hoke. She provides all the details behind my brief summaries.

Dave


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## browninkie (Jul 15, 2014)

Ooh, I didn't even think about refining a second time. Very good pointers~~ Thanks Dave.

I've been searching about sodium thiosulfate and it's ability to dissolve silver chloride, but I didn't find too many information regarding the silver recovery from the silver/thiosulfate solution. I read about a technique that involved a rotating silver drum with a negative cathode.. which sounds really complicated  
I also read briefly about using steel wool to cement out the silver? This process seemed feasible but I couldn't find any info about the actual process.
Are these my only options of recovering the silver?
Or is there a simpler method of cementing out the silver from the solution?? 
Any additional sources or links regarding sodium thiosulfate would be really appreciated


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## Palladium (Jul 15, 2014)

If your talking about agcl you can use the sodium hydroxide/sugar method, or hcl/zinc- aluminum foil method, or you could use iron and sulfuric acid. Their are many methods it's just according to where you coming from and where your going with it.


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## browninkie (Jul 15, 2014)

Hey Palladium,
I was researching using AR to remove stones from jewelry and a common problem was that AgCl stops the process.
Therefore, people used either ammonium hydroxide or sodium thiosulfate to dissolve the AgCl crust before proceeding again with the AR.
Now, this is where I'm hitting a wall..
How am I supposed to recover the silver that was dissolved in the sodium thiosulfate solution?
People mentioned using steel wool to cement out the silver or this rotating SS drum cell contraption, however I couldn't find any detailed information about these processes and was hoping someone could point me to the right direction..


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## 4metals (Jul 16, 2014)

The silver contained in the thiosulfate is not as easy to recover as silver dissolved in ammonium hydroxide. If you are producing a lot of the thiosulfate it pays to set up a flow through steel wool canister system and smelt out the silver when the canister fills up. 

If you are only processing a small amount, the ammonia used to clean up the gold encrusted with chlorides can be acidified with HCl to drop silver as a chloride. The silver chloride can be collected and when you have enough it can be reduced to silver method by any of the methods already outlined on the forum. 

Ammonia tends to fume a lot, the genie in the bottle as I like to call it. The thiosulfate has no smell or fume. It's a trade-off. Small quantities, deal with the fume and recover the silver quickly. Larger quantities the thiosulfate method is more advantageous even though the recovery is more difficult.


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## browninkie (Jul 16, 2014)

Thank you very much 4metals~ just the answer I was searching for.
Early on, I decided not to use ammoninium hydroxide because of its fulminating properties with metal salts. :shock: 
However, the process you mentioned looks good so I'll keep reading about safely handling NH4OH.
Thanks once again~~


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## 4metals (Jul 16, 2014)

Never store ammoniacal solutions with silver in them, always acidify them with HCl, this will drop the silver chloride and eliminate the potential problem of forming silver fulminates (which are explosive)

Many years back I had a client in the west who was a bucket refiner, he had buckets everywhere, some with solution and some with crust. Thank God this happened on a weekend but one of those crusty dry buckets was ammonia and silver which blew the wall of his refinery out of the building. No one was hurt, or even close by, but that was 100% luck. Storing silver in ammoniacal solutions is a bad practice. After the silver chloride dissolves, decant the solution and add HCl and you will never have a bucket that goes boom in the night.


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## butcher (Jul 16, 2014)

Also keep the ammonium waste solutions separate, and treat it separately from the other waste you produce (acidic waste of metal solutions), where mixing of the two can again form a dangerous solution or situation, during the process or in treatment of these wastes.


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## luca (Oct 31, 2014)

Dear Sirs.

FIOA INTERNATIONAL Have made a machine for this purpose:

http://www.fioainternational.com/en/macchinari-per-orafi-goldsmith-machines/decastonatura-chimica-pietre-preziose-chemical-precious-stones-removal/scastonatura-chimica-pietre-preziose/


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## luca (Oct 31, 2014)

FrugalRefiner said:


> browninkie said:
> 
> 
> > This is what I was leaning towards. Which got me wondering about the process..
> ...



Here is the solution: 

http://www.fioainternational.com/en/macchinari-per-orafi-goldsmith-machines/decastonatura-chimica-pietre-preziose-chemical-precious-stones-removal/scastonatura-chimica-pietre-preziose/


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## g_axelsson (Oct 31, 2014)

luca said:


> Dear Sirs.
> 
> FIOA INTERNATIONAL Have made a machine for this purpose:
> 
> http://www.fioainternational.com/en/macchinari-per-orafi-goldsmith-machines/decastonatura-chimica-pietre-preziose-chemical-precious-stones-removal/scastonatura-chimica-pietre-preziose/


Interesting, what principle is it based on? Which chemistry? Mechanical?

Göran


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## kurtak (Oct 31, 2014)

looks like a fume hood with standard glassware in it to me :lol: 

How much $$$$ do they want for this "Stone Removal Machine" :roll:

Kurt


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## 4metals (Oct 31, 2014)

I believe Mr Luca is an employee of the manufacturer, just my guess. If you are Mr Luca we invite you to post your wares for refining in the Refiners section in Miscellaneous. No other manufacturer has done that to date and it is a shame because that is where it belongs and I for one would like to see it there.


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## luca (Nov 3, 2014)

Dear Mr 4metals, i am new on this gold refining forum and i was just thinking that it can be useful for people interested in gemstone removal to learn more about this machine and technology.
Anyhow i understand the rule, if we are allowed to post equipments and machinery only in the refiners section in miscellaneous, i will follow your instructions.

Many thanks and Best Regards



4metals said:


> I believe Mr Luca is an employee of the manufacturer, just my guess. If you are Mr Luca we invite you to post your wares for refining in the Refiners section in Miscellaneous. No other manufacturer has done that to date and it is a shame because that is where it belongs and I for one would like to see it there.


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## luca (Nov 3, 2014)

Dear Sir,

Chemically the system uses aqua regia to dissolve the gold parts holding gemstones, and once the stones are removed it is possible to recovery fine gold by precipitation as well as wash out the stones covered with silver chloride.
The unit is compact, including one or two etching reactors, vacuum filtration section and gold precipitation section with magnetic stirrer.
All is controlled by the switchboard (heaters, vacuum etc) and the fumes are washed directly in the hood thanks to a recycling tank connected to a proper fumes recovery area in the hood itself.
For further info you can contact the company.

Best Regards


g_axelsson said:


> luca said:
> 
> 
> > Dear Sirs.
> ...


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## 4metals (Nov 3, 2014)

Thank you Mr. Luca

I think links to your different equipment in the refiners section would be useful.

You are also more than welcome to respond to any posts with your expertise and reference any equipment but we would appreciate the commercial type links to advertisement or equipment you manufacture be in the refiners section.


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## g_axelsson (Nov 3, 2014)

luca said:


> Dear Sir,
> 
> Chemically the system uses aqua regia to dissolve the gold parts holding gemstones, and once the stones are removed it is possible to recovery fine gold by precipitation as well as wash out the stones covered with silver chloride.
> The unit is compact, including one or two etching reactors, vacuum filtration section and gold precipitation section with magnetic stirrer.
> ...


Thank you for your answer.

I'm a bit disappointed though, it seems to be nothing else but a fancy digester and some plumbing for moving liquids. I was hoping for a novel approach to dealing with high silver content gold alloys, some way to break down the passivising silver chloride covering.

Regards, Göran


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## 4metals (Nov 3, 2014)

Goran,



> I was hoping for a novel approach to dealing with high silver content gold alloys, some way to break down the passivating silver chloride covering.



Filter the acid containing the silver chloride coated metal, I prefer to do a coarse filtration through a plastic screen so the loose silver chloride will pass through leaving only the chunks of silver chloride coated gold and the stones in the screen.

A lot, if not all, of the stones will have been dislodged so select a mesh that will not allow the smallest of the diamonds, those pesky little 1 pointers, to fall through. 

Now tumble everything in the screen in a saturated solution of sodium thiosulfate. This will dissolve the silver chloride and leave you with a shiny gold surface where the silver chloride has stopped the work of the aqua regia. Small rock tumblers work well or a plastic wide mouth jar sitting on a pair of rollers. 

If the chlorides are heavy it may require one or two tumbles to complete the process. This process has no smell and it need not be done in a hood. 

Pass the solution through the screen again and rinse well. The gold will be a bright yellow if it is done. The stones will be loose and clean, just requiring a good rinse. If the gold still has stones set in it they can often be mechanically removed as they are likely loose. If required the gold can be put back in aqua regia for further digestion. 

Most prefer to spend some time to remove any loose stones mechanically and melt the gold into a button. Commercial refiners use an XRF to find the gold content and pay on that plus the gold that comes out of the aqua regia. 

Since the gold coated over so severely, it is easiest if you want to recover it completely to inquart the button in silver and do a nitric dissolve.

The silver chlorides that fell through the screen on the first coarse filtration can be filtered out and collected and reduced with caustic and sugar to produce a metallic silver with a minor percentage of gold when assayed. Easily cleaned up in a silver cell. 

(edited to add the last paragraph.)


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## justinhcase (Nov 3, 2014)

In my little cell all you have is a very fine cell slime and stone's.
I just feel through the filter paper for the stone's and put all the left over's in my next inquartation.
I always ware glove's and just wash them back into the paper when I am finished.
I will have to try a small screen before the filter instead.


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