# How to clean diamonds after a stone removal process



## ilzho (Mar 15, 2013)

Hello:

I am helping a pawn shop sort his diamonds he received back from the refiner.

The diamonds are melee and are coated with a black like substance and I need help on how to get it off. There are no black diamonds in this lot, they just appear this way from the black coating.

Not sure if an ultrasonic cleaner would work or help, but it might be silver oxide attached??
Do I need to cook them in some chemical?

Please see the attached pictures.

As you can see they are dark from this material/chemicals. 

Any help is appreciated.


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## Dan Dement (Mar 15, 2013)

I buy and separate quite a few hundred carat lots from Pawn Shops. First, it looks like lots of these stones are Cz"s that have been soaked in HF. These are the heavy frosted goods that you think are coated. What I would first is weight all the stones together and write it down. Next I pull several of the bigger coated stones and mm the stones and weight them. Very easy way to see if you are dealing with frosted CZ's are coated diamonds. CZ's weight about 50% more than diamonds do. I believe the majority of what you think are coated are Frosted Cz's from HF Acid. If this is the case, you know what your dealing with. If you don't know how to mm the stones and check the weight, I will do into more detail. The truth is, if you don't know how to do this, you really don't have the skill to separating out the diamonds. 

If I am right, you first really need to stones and the best way to do this is in small wire screw together cleaning baskets. You load the wire baskets about 3/4 full and drop them into a ultrasonic cleaner full of heavy duty jewelry cleaner like Oakite. Run the ultrasonic for about 45 minutes and then remove the baskets and wash the baskets with clean water. After rinsing, while the stones style in the baskets, put them thru the Steam cleaner. Hold the basket with tweezers or salad thongs and blast them thru the basket until the stones easily move around the basket. At this point, you should have semi clean diamonds in the small baskets. At this point, I take a small hair dryer and blow dry the diamonds. Use the Salad thongs as the baskets get pretty hot quick. I then get a clean clear beaker and open the baskets and empty the diamonds and use the hair dryer to remove the moisture from the diamonds so they diamonds easily move around in the bottom of the beaker. Careful not to use too much force as .005 diamonds will blow out of the beaker. You will know when the diamonds are dry as they will not stick to the bottom and clump together in groups. On to the separating.

Next, I check my weight and see how many I lost and go look for them. I take the clean stones and separate them by broad sizes using a diamond sieve. I take a large clean calendar blotter and separate the diamonds into 4-5 piles. Best to have several small diamond shovels and a Platform loupe which is a diamond melee loupe of a stand. You need lots of light, head loupe, and good tweezers. I first separate out the CZ's, Color, and diamonds. If you start with the bigger stones like the 3.0mm which will be close to .10 points, separate out frosted CZ's from the clean diamonds. I put them into a line and take out the frosted cz's and put them into a pile. As you work down in sizes, it will get easier. If all the stones are near the same size, if you are unsure and it's a 2.9mm and weights .09, then it is a diamond and if it weights.16 you got a CZ. Throw the color into a separate pile and have fun. When you get down to .01, you will have gotten fairly good at it. Now, I separate out the Brown's, single cuts, fancies in their own piles, the keepers, and the junk. 

Long Winded yes but that's what it takes. Next, I get my 150 carats of what I keep in stock and if I bought 100 carats, I prepare to sell 100 carats. Keep the good, sell the bad. If the diamonds were not soaked in HF, I recommend to get your refiner to do it for you. Really makes separating out the CZ's a breeze. PS, I buy melee usually in the $85. to $125 a carat. No, I don't pay for CZ's. Got to see it to price it. 

Dan


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## ilzho (Mar 15, 2013)

Thanks for the information, I appreciate it.

I separated most of the frosted CZ's out of the lot. What you see is just a small sample. I have a about 80 cts and counting and most are under .05ct.

I know most are diamonds as I see some inclusions/shadows inside the diamonds through the gunk. I put them underneath my microscope, so I can verify that most are diamonds.

Now, that isn't to say there aren't czs in the picture; I'm sure they are, but I would rather make sure when they are clean to make that determination. The CZ's that are frosted or that have started to blister/frost, they go in the trash pile .

I was unsure if the ultrasconic cleaner would be strong enough to clean the chemicals off of the stones from the stone removal process. I'm just not sure how the refining process works and what chemicals are used as this would help me understand a little more.

I will try your recommendation.

Thank you!


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## nickvc (Mar 16, 2013)

I have to say that the stones look like they have been smoked, does your friend or refiner melt the metals first and treat the used flux with HF to recover the stones if so they need recutting which lowers their value considerably. To recover the stones without damage they need to be put through very hot acids, I start with nitric to eliminate any silver settings and to start to attack the silver and base metals in the mounts and then onto AR which is used extremely hot, even this method will not dissolve all the metals but should loosen the settings enough to be able to easily remove the stones.


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## ilzho (Mar 16, 2013)

I am not sure.
The large stones are fine, but the small (melee) are coated. I will try to check and see what the whole stone removal process is.


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## Dan Dement (Mar 16, 2013)

Nick,

I soak my own in HF but I sure am not going to recommend him doing that. If they are smoked or burned, he is going to have to repolish the goods or deep boil them which is beyond most of our capabilities. If he can establish if they are Cz's or diamonds by weight, lots of Indian's will buy the burned goods. Price of the burned goods is under $50. per carat and not a lot of demand for it anyway. I buy at least 100 carat a month of goods from a Pawn Shop Buyer who acid removes his stones and the goods look similar. A strong cleaner like Oakite will remove most of the crud but if the goods have not been Hf'ed that really needs to be done. In line with GF rules, I recommended his refiner do it. Nothing I can think of is as much fun as sorting 50 carats of .01's & smaller to make you realize that 1. Your Old 2. Your eyes are really gone anyway 3. Appreciate the cutting skill of somebody 4. Be glad that you don't have to set all of time 5. All the buyers want the bigger stones anyway.

Old Jewelry Dogs Complaining to each other!

Dan


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## nickvc (Mar 16, 2013)

Dan I'm with you I use HF very very cautiously and don't suggest anyone get near the stuff but I was asking how they treated the scrap to recover the stones, it's not rocket science but is hard to perfect if anyone ever really does. I also know what you mean about sorting small stones, I need a 10X loupe to see 25 pointers these days :lol:


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## ilzho (Mar 16, 2013)

So the HF acid damages the diamonds. Is that true?


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## Dan Dement (Mar 16, 2013)

No, HF damages almost everything else except corundum. However, HF is EXTREMELY dangerous and can easily kill you. It does not burn you like most acids and gets into your bones and eats away the bones. A very small amount internally can kill you also. GRF has a policy not to encourage or talk about it. I am not sure where you are located but I will clean and process your stones for you. You can also go to your refiner and most will soak your stones for you. You say you have a microscope but do you have a Diamond Sieve, MM gauge, small wire baskets, ultrasonic etc? 

Dan


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