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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