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 » RockyTalky
»  » GIA color master stone set...
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GIA color master stone set... |
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| P: 6/1/2006 8:18:02 AM | |
Cullinan Rough Rock Total Posts: 13 Last Post: 1/16/2007 Member Since: 7/16/2005 |
IĄŻm looking for GIA diamond color master stone set.
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| Posted: 6/1/2006 8:18:02 AM | |
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There are 3 replies to this message. There are 3 replies on this page. |
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| P: 6/1/2006 9:20:46 AM | |
oldminer Ideal Rock Total Posts: 4,964 Last Post: 11/20/2009 Member Since: 9/4/2000 |
Maybe some newcoming gemologists will have heard of any diamond houses that still try to supply GIA Master Diamonds for grading sets. It is a very difficcult thing to put a set together. Either the cost from a regular supplier will be very high or the work of submitting diamonds to GIA for a set will be very slow and highly difficult. GIA will reject many good diamonds before selecting one they feel is qualified. Once a stone or two has been assigned to a set, you have to find others that suit the set and it even becomes more of a challenge. Over the years, we have purchased three or four existing sets for lab use. They are pretty much irreplaceable. I lucked out a few years ago when I bought these two: A 1 carat Y-Z and a 1 carat W-X. Both had older GIA full reports. They have proved to be very useful in watching the GIA standards change incrementally now calling these fancy and light fancy color diamonds. We also use master diamonds to calibrate CZ desk sets used for daily grading work. CZ's are useful when used in fixed and known lighting environments, but they often change color, so having diamond masters is still essential. Diamonds must be used for masters when travelling as CZ's change color with different lighting in ways that diamonds would not. Best of luck. David S. Atlas |
| Posted: 6/1/2006 9:20:46 AM | |
| P: 6/1/2006 12:46:07 PM | |
adamasgem Ideal Rock Total Posts: 1,310 Last Post: 11/2/2009 Member Since: 5/23/2003 |
Date: 6/1/2006 8:18:02 AM Author:Cullinan IĄŻm looking for GIA diamond color master stone set. If you are in the trade, complete or partial master sets, are available from Lazare Kaplan in NYC, among others... Marty Haske GG(GIA), Senior Member NAJA, ISA Appraisal Trained(past ISA), BS(MIT)/MS(MIT) |
| Posted: 6/1/2006 12:46:07 PM | |
| P: 6/1/2006 1:15:36 PM | |
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adamasgem Ideal Rock Total Posts: 1,310 Last Post: 11/2/2009 Member Since: 5/23/2003 |
Another fact you may not know is that the positioning of the color grade separation(s) is not always uniform, although you might be led to believe it so, ie an EXACT E, F, G, etc...stone that separates the border , in the case of an E master, between a D and an E. At best, based on data I have been given in the past, the best postioning is visually quantized to 10% of a color grade range, and based on that finest quantization, the expected on sigma difference between the nominal position and the best estimated position would be about 16% of a color grade range (17 stone sample set statistics Nominal versus best estimated position). Surprisingly, to me a long time ago, what I was told was an "E" master was 20% into the E range, a blessed "H" I had was 30% into the "H" range.. It is not an "exact" positioning.. GIA used to give this finer (10% quantization) numbers to AGS members only, I don't know whether they still do or not. Marty Haske GG(GIA), Senior Member NAJA, ISA Appraisal Trained(past ISA), BS(MIT)/MS(MIT) |
| Posted: 6/1/2006 1:15:36 PM | |
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