Removing stones

Greetings.

First I want to say that I did search the board and google before I posted and was unsuccessful. However, being a bit of a newbie on this forum despite reading for a long time, I do want to apologize in advance if this is a well covered question already. I've followed most of lasersteve's posts but my question seems to be a little outside of that box.

I want to remove bagget and round diamonds from my gold jewelry. I know that the large refiners use a chemical process for this. Does anyone know what that process is?

I'd really appreciate it if someone would share it with me - whether it's dissolving the gold from the stones or dissolving the adhesive (?) if that is what is used. I didn't jump into dissolving the gold because I didn't know if the processes that are typically used would damaged the diamonds.

Thanks,
GOY

GOY,

True diamonds will survive the AR acid bath and torching.

If you do not want to harm the jewelry they make a stone remover for jewelry. I think it's called a 'pro lifter' or something like that. A friend of mine has several.

Here's a link on diamond removal:

Diamond removal


Steve

You consistently impress me with your body of knowledge....

What about stones other than Diamonds. Will they survive AR.
Thnx,

Emil

diamonds rubies opals sapphires do OK, pearls are toast
emeralds lose their shine if they were oil enhanced, now legally the emeralds are not supposed to be oil enhanced and emeralds that were not come out fine but if they were enhanced the finish has small micro cracks which were disguised with the oil enhancing. I've been told the emeralds can be re-oiled but I don't know the technique. If you need details on cleaning up the stones and separating the stones from the chlorides, let me know and I'll tell you a technique.

Thanks for the information 4metals. I will keep you in mind when I need that information.

Thanks for the quick responce.

Emil

One of my customers was a pawn shop. They removed stones larger than 20 points, but the small ones came to me in the scrap jewelry. They are not glued in, they are held in by prongs, or are bead set. The holding devices are easily cut with a small abrasive parting disc on a flex shaft. That way you can avoid chemical processing and chasing the diamonds.

In order to trap the fine metal particles that are generated in the process, and to insure the stones were not lost, I made a simple "glove box" from a short piece of 6" pvc pipe. I removed a portion of the side and installed a plastic window so I could see my work. The stones can be removed quite rapidly once you get a rhythm.

Harold

It's pretty funny that you mention a pawn shop as that's where a lot of my material has been coming from as well. I think the glove box is a great idea. Did you use an abrasive disk on the bead set items, or just the prongs? (as I google bead set, lol).

By abrasive disk, did you mean a cutting wheel or something more along the lines of a gasket removal pad in the 100-300 grit territory? I just want to make sure I'm on the same page given that I'm the slow one in the group :lol:

The labor involved to physically remove anything but prong set stones is huge. I have been involved with stone removal for 4 different refineries over the years processing lots as small as a few ounces to over 1000 ounces and they were all processed in aqua regia, the stones were cleaned by tumbling is sodium thiosulfate, and after a minor amount of picking out of the undissolved pieces the stones were clean and shiny. Occasionally a lot was slow to dissolve, it was usually associated with an Indian manufacturer, they love their silver in the alloy. But for the most part they are easy dissolves.

GOY said:

It's pretty funny that you mention a pawn shop as that's where a lot of my material has been coming from as well. I think the glove box is a great idea. Did you use an abrasive disk on the bead set items, or just the prongs? (as I google bead set, lol).

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Yes, on the bead set items as well, but as 4 metals alludes, that is slower than removing from prongs. Not generally as much metal retaining the stones, but it's harder to access.

By abrasive disk, did you mean a cutting wheel or something more along the lines of a gasket removal pad in the 100-300 grit territory? I just want to make sure I'm on the same page given that I'm the slow one in the group :lol:

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I don't think you're slow----you just haven't been around jewelers, so you'd understand how they work.

The discs I spoke of come from jewelry supply houses. They are commonly used in that trade. They're a resinoid bonded disc, about 1/64" thick, so the kerf is quite small, minimizing losses. They are mounted on a tiny arbor that has a screw in the end. The supply house will have them, too. They are available in two sizes, as I recall. One of them is about 1" diameter, the other slightly larger. It has been years, and my memory has dimmed. I do recall that they last a long time if you don't break them. They're surprisingly tough, however.

I agree that acid removal is fast and good, but if you inquart your gold to process, that complicates things a little. Still works, and, in theory, diamonds are not harmed by the melting process. You have to fish them out of the remains, which often include some silver chloride. For me, it was best to manually remove the stones. They were not returned, so they provided extra profit and more than paid for the time it took to remove them.

An added thought. Even small, broken diamonds have value. Not a lot, but it if you find chipped diamonds, save them until you have enough to ship. I used to get paid $25 carat for them. Better than tossing them.

Harold

I have never seen anyone melt jewelry with stones in it to inquart before refining. The jewelry is put up in acid as is. As I said it dissolves well enough to remove the stones on most lots. A glove box and abrasive disk is a great idea for the few pieces that don't dissolve completely.

4metals said:

I have never seen anyone melt jewelry with stones in it to inquart before refining. The jewelry is put up in acid as is. As I said it dissolves well enough to remove the stones on most lots. A glove box and abrasive disk is a great idea for the few pieces that don't dissolve completely.

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Yeah, I understand, but my operation revolved around inquartation. I preferred that to fighting with alloys that were troublesome. That's why I used the abrasive process for removing stones.

I didn't like the results I achieved without inquartation, although the only thing I processed that way was filings. Even they got a prolonged boil in nitric, where a great deal of contamination was removed, but the end product always left a great deal to be desired.

I was a quality freak, so I re-refined my gold, although my gold with a first refining, aside from filings, was always quite good. I chose to re-refine to insure that my customers received no less than industry standard. The improvement in quality was very noticeable. My gold, prior to a second refining, always had traces of oxides, but I could melt my twice refined gold without flux and still have oxide free gold. The only flux I used was to line the melting dish, so the gold would flow freely.

By now you've probably seen the picture, below, more than enough times, but his is an example of gold I turned to shot. It was melted exactly as I suggested, and was not pickled for appearance. I firmly believe I bordered on 4n quality, although I never made the claim.

Harold

Harold and anyone else:
When you speak of quality as 4n's do you mean 99.99% or 99.9999% when you refer to pure gold?
As a newbe and one not familiar with the trade, I find many of the terms used for gold to be confusing. We refer to pure gold as 24k = 100.00% pure, but in reality, all gold is contaminated to a degree.
I have read that 24k can be hallmarked up to 1/2k% low or 23.51 - 24.0k.
Now add terms like:
Fine Gold,
Bullion,
Solid Gold,
Spot,
I understand that these terms are ranges, but I don't find anywhere in the forum where they are explained. So if you want to describe what you are buying or selling, then it would be nice to know what the trade accepts as their standard for terms.
That way at least one would know what the buyer is telling you when they set a price representing their value of the gold you are offering for sale.
This information might well become a stickey, because I'm sure I'm not the only one that is confused by all the terms thrown around.
By the way. I never tire of seeing that picture and only hope someday I can produce a product that equals it. A lofty goal to reach for, I know.
Sorry to be so long and thanks in advance, I really appreciate all the quality information that I have learned since finding this forum.

4N gold is .9999 fine, however that is 99.99% pure. I know that seems confusing on the surface until you understand it is referring to 9,999 parts in 10,000 being gold. Percentages are parts in 100. So if you had a mass of gold that was 99% pure it would be .99 fine or 2N gold.

As to karat gold it is worth mentioning that you are starting with the assumption that 24 karat gold is pure when you allow the ½ karat under karating. As long as the gold is the smallest amount over 23 parts in 24, it is still 24 karat. You can be sure jewelry manufacturers take advantage of that, such a difference adds up quickly in volume. If you have a piece of jewelry that came from a country that allows hallmarking to vary by ½ karat expect a piece marked 18K to be just a fuzz over 17 1/2K, that is when they are honest.

Careful testing is the only way to be sure when buying. I admire your desire to be honest in your selling.

Fine gold is typically defined as .999 fine, but has been used elastically so usually you see “.999 fine gold” denoting the actual fineness.
Bullion only means gold in bulk form typically for investment as bars and rounds. You can find it in different purities, but usually not under .900 fine.
Solid gold is gold that has the same purity throughout the piece (instead of rolled, plated, or filled).
Spot is the current market price of the metal, typically listed on the Comex or London Bullion Exchange.

I hope that helps.

In addition to Oz's comments, it might help you to know that the industry standard for fine gold is 9995. That is an excellent target as a minimum where purity is concerned. Achieving 4N is not easy----although processing in a gold cell makes it easily within reach.

The connotation 24 K indicates that the gold is not intentionally alloyed, so it does not necessarily reflect on purity. Traces of contaminants, so long as they are less than 2%, would not change the legal description.

Handling of gold after it is refined is probably the biggest source of contamination, so learn and use clean work habits if you refine. Always eliminate base metals as early in an operation as is practical. The end results will generally show the difference.

Never avoid the washing cycle of precipitated gold. It is the last opportunity to remove unwanted substances. The chance of improving quality in the furnace is not good unless the Miller chlorine process is employed. The hazards of the process make it not worth the effort for the home refiner.

Fine gold should be able to withstand a melting without flux, and remain bright and shiny.

Fluxing gold in the furnace will not drastically improve it's quality, removing only the oxides of metals. Any that is not oxidized is simply combined with the gold, with the flux masking the symptoms.

Harold

Fineness is defined in the trade as parts per thousand.

Therefore:

4 nines gold = 999.9 Fine = 99.99% pure.
3 nines eight gold = 999.8 Fine = 99.98% pure.
3 nines five gold = 999.5 Fine = 99.95% pure.
3 nines gold = 999 Fine = 99.9% pure.
2 nines gold = 990 Fine = 99% pure.

99.9999% pure gold is 6 nines or 999.999 Fine

Just count the total number of nines.

There are some people on the web that believe that you only count the 9s after the decimal point when purity is expressed in percent. Thus, they think 4 nines is 99.9999% pure. This is totally wrong. I found this error to be common on colloidal silver sites.

I understand your point GSP. Adding to the confusion is the marking of 3 popular 4N gold coins.

The US Buffalo is stamped “1oz .9999 fine gold”.
The Canadian Maple Leaf is stamped “9999 fine gold 1 oz or pur” (no decimal point).
The Vienna Philharmonic is stamped “1 ounce gold 999.9”

To make it more confusing, there is "fine gold" and Fineness, which is abbreviated "Fine". "Fine gold" is loosely defined by the dictionary as gold that is almost pure. In the trade, "fine gold" is at least 99.95% pure.

Whoever designed the US Buffalo obviously didn't know what he was doing. I would think that, strictly, .9999 fine gold means .09999% pure. I guess they could have based it on 1.0000 being 100% pure but, if so, they would have had to create a new convention.

The Philharmonic is marked correctly, although I think it should have the word "Fine" after the 999.9.

The Maple Leaf could be read as "four nines", "fine gold", which would be a correct statement. The 9999 could be read as "four nines".

Do you remember the jeweler/refiner from Colorado that was on the forum awhile back? He was minting coins and marking them as .999 or .9999 Fine. I think I said something to him about it, at the time.

In Europe, carat (I think that's how they spell it over there) gold is marked in Fineness: 18K is 750 and 14K is 585.

I know all this sounds picky but, to carry on a non-confusing conversation, we should have our terms straight.

BTW, according to several websites, the lowest purity that can be legally called 24K is 99%. That is 1% under.

Harold,
It is interesting to me that you prefer to inquart karat whenever you can. I have successfully refined thousands of ounces of karat gold without inquarting. Here in the East refining rates are competative and the most a refiner can hope to charge is 2%. Possibly for that reason I have never inquarted for standard aqua regia refining of karat gold. The expense of the nitric dissolve on top of the aqua regia dissolve adds to the cost. There were some precautions however. All karat gold (except stone removal) is melted and assayed for gold and silver. When a refining lot is put together, the goal is 7 1/2 % silver or less, this substantially decreases the chances of a lot coating up with chlorides and stopping the reaction. In a typical refining lot of 1000 ounces, the remaining undissolved shot averages out at about 2 ounces. The customer is paid on assay so he has been paid for the entire content of his job. The 2 ounces is tumbled in sodium thiosulfate to dissolve the chlorides and melted into a button to be included in another refining lot, it always assays at a higher gold percentage than the lot it was in as alot of the base metals have been leached out. Another trick to gain purity in the precipitation is chilling of the loaded aqua regia. If the acid is cooled to 50 degrees before filtering (ice works for this) the solubility of any silver chloride dissolved in the warm acid drops way down so it can be filtered out easily. The gold is dropped with sulfur dioxide gas, the nitric is driven off by gassing because we never use urea in a system of my making. The gold is transferred to a polypropylene lined cement mixer and tumbled slowly while rinsing, it is washed in distilled water, followed by hot distilled water rinsing. The sponge is transferred to a large Buchner funnel and sucked dry and melted. The tumbling improves rinsing dramatically as the gold packed in a filter tends to channel the rinse waters leaving some sponge poorly rinsed, with good vacuum all of the decanted rinse waters are filtered quickly so there is no fear of losing small particles of gold with the changing of the rinses. Gold produced by this method consistantly assays .9997 plus (Ledoux ICP) after melting. We claim .9995 and nobody ever has challenged the purity. We only have to drop once, our accountability is 99.7% in the resultant shot and the silver chloride is reduced with sugar and the resultant bar is 97 to 98% silver and the gold in the chlorides approaches 2% on average. Adding in the gold content of the undissolved button and the silver bar the overall accountability approaches 99.9%. The resultant waste treatment sludges always have payable gold as do sweeps from burning papers used to wipe up drips and filter papers so the roughly 3/4 of an ounce of fine "lost" on each 1000 ounce refining lot turns up eventually.
I have owned a facility producing fine as described above and engineered 3 more refineries and similar results have prevailed. That is why, for the most part, I don't inquart with karat gold refining. As I have posted in the past I have set up a process where inquarting silver, for the purpose of refining silver via sodium formate reduction, gives me a easy high purity gold residue for subsequent refining. That product dissolves in aqua regia with nary a trace left undissolved.

Lets see if I'm understanding what your saying.
From Lou:
Fineness is defined in the trade as parts per thousand.

Therefore:

4 nines gold = 999.9 Fine = 99.99% pure. ( = Fine Gold)
3 nines eight gold = 999.8 Fine = 99.98% pure. ( = Fine Gold)
3 nines five gold = 999.5 Fine = 99.95% pure. (= Fine Gold)
3 nines gold = 999 Fine = 99.9% pure.
2 nines gold = 990 Fine = 99% pure.

99.9999% pure gold is 6 nines or 999.999 Fine
Then:
Fine Gold has to be 99.95 or more pure
24k = 1.0000 fine = 100.00pure = 1000.00Fine
23k = 0.9600 fine = 96.00pure = 960.00Fine

To claim spot with no deduction gold would have to be 99.9999 pure
I would expect the bullion at Ft Knox to be 99.9999 pure then.
Then: Gold fingers processed AP, Nitric wash to remove base metal and HCL-Clorox, or AR, then HCL wash and distilled water washes should get the gold close to 99.98 or 99.99 pure.
I would think that a buyer would buy that gold at a price close to the 95 to 98% of spot that I see on the web sites.
Does this make sense or am I missing something?
Thanks for all the explanation from all.