2006 GIA grading report - Post info here please
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by JohnQuixote » January 3rd, 2006, 12:23 pm
I love it. 10:20 AM in Oz. Garry is up like a shot, bathed, coffee in hand & ready to calculate! |
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Well i did think the release date was yesterday John?
Am I too early? 
Even warmed up the old DiamCalc program 
Garry Holloway FGAA DipDT
HCA and Ideal-scope developer http://www.ideal-scope.com and http://www.HollowayDiamonds.com.au |
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I have not seen the newest Reports yet. What I find interesting is that before the release, they made some slight changes to the reports, I believe as of October or so of 2005.
The format for the certs is the same but the insert page for the vendor includes total depth, table size, crown angles, crown height, pav angle, pav depth, star length %, lower half %, and all the other usual suspects. I think since they started on the 3rd, the industry will not likely receive them until GIA shuffles them through the wheels of their bureaucracy, but I'd be curious to see them as well if anyone does have one in already! Anyone have the GIA Sarin updates for the cut grades? |
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I have seen the Sarin-update, and I think it is very dangerous. Since most cutters, working with GIA, lack the cut-grading-background, which is common knowledge here on Pricescope, I fear that many will rely on the proportion-suggestion of Sarin, after scanning the rough stone. Since Sarin calculates for the stone with the highest weight, and since the GIA-grades are too wide on the steep-deep-side, this will probably result in a very high supply of newly graded GIA steep-deeps. If so, in totality, the average cut-quality of GIA-rounds will deteriorate, and not improve. Live long, |
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I am a new poster, but I was working with the new GIA online cut grading software this morning from 5 to 7 AM EST USA. Wow, what a program! Alot of confirmation of HCA but it seems to capture excellent in some cuts you wouldn''t quite expect and then where the HCA is less than 1 some none excellent replies.
I was mainly concerned because I just bought a diamond based on HCA (0.9 EX,EX,EX,EX)which is being shipped and I will subsequently get appraised. I was worried about the shallow crown of 14%, but if the certificate is correct and the other measuremnets are OK which unfortunately is in % not angles, I may be getting a very nice stone at a lower price than is typical. My reverse calculations, considering the crown % can actually vary between 13.5 to 14.4, is therefore 32.7 to 34.4 degrees. If it is 33 degrees or more, the GIA program gives this diamond an excellent. Less than 33 % Very good. Unfortunately there were a couple of parameters like star length %, etc. where I had to use a default number. The vendor has told me this is a beautifully cut diamond( eventhough not the traditional ideal cut), and looks good under the idealscope, so I am going with my gut and trusting him that it won''t be a shallow crowned dark diamond. Bill |
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Garry, this is OT but Paul's comments made me think of this. Here's a clip from an AGS "ideal" with the new performance-based report. Without evidence, I expect that you guys wouldn't have believed that a 35.1 / 41.0 stone would have made the grade like this.
What do you think? It is that much different than what Paul is predicting will result from the new GIA ranges?
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Hey Elmo, Nice example of a borderline AGS-0. Definitely not my favourite combo, but with the correct length of lower girdle-facets, this can definitely still get the AGS-0-grade. Now increase that pavilion angle to 41.6, and you will still get GIA-Excellent, even with a crown-angle of 35.5°. In AGS, such a combo would be an AGS-4, according to the AGS cutting-charts. And the Sarin-software constantly suggests such combos, when running it on a rough stone with sufficient depth. Imagine the flow of these goods coming on the market. Live long, |
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I was afraid of that. hopefully it wont happen but im not holding my breath. |
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In Elmo's example a 36 degree CA with a 41.0 degree PA gets Ex as well.
Not important, but the order of input on the interface is different than when it came out. Total depth to the bottom next to the GT option now (screen shot on the right is current).
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...Did you leave milk & cookies (and a loupe) next to the hearth the night before the release? THAT would be in true cut nut fashion. |
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Good find Elmo. I think Paul is on the money. AGS charts give this stone a 1, but if it was tight on symmetry then it is possible for it to be nice. It is also possible to fiddle with the idexing and paint the crown or pavilion facets and improve it by reducing the leakage. Sir John; is GIA bringing good cheer? I am not a cutter - i think GIA might be making it that bit harder for me to find nice ice. I left the fire on last night.
Garry Holloway FGAA DipDT
HCA and Ideal-scope developer http://www.ideal-scope.com and http://www.HollowayDiamonds.com.au |
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wink, nod  and Bump Has anyone seen any new round stone reports with cut grades?
Garry Holloway FGAA DipDT
HCA and Ideal-scope developer http://www.ideal-scope.com and http://www.HollowayDiamonds.com.au |
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I''ve seen pavilion angles heading down to 41.2 and still getting ideal rating. It was a 34.5/41.2 combo but was still a little suprised to see it get the full out ideal rating, HOWEVER the stone did happen to be a really nice looking stone (HCA of over 3 too if memory serves me right). I''m hearing what you''re saying Paul about the recutting options. One positive I guess is we''ll be able to test, see and compare how one of these apparent steep/deeps looks next to other GIA/AGS ideals and whether it holds water or not when it comes to observation testing. Knee jerk reaction tells us all it''s a crapper but until I''ve done some observation testing with it, only then will I draw a more concrete conclusion. I don''t want to make any hasty judgements at this time. We should be getting some of the new reports next week however I''ll be taking in some sun down by the British VI''s. :) If nobody has posted any examples till then I will when I return on the 17th. Peace, |
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DiamCalc will give aGS candidate grades - but not from a scanned 3D file - only from manually entered data
Garry Holloway FGAA DipDT
HCA and Ideal-scope developer http://www.ideal-scope.com and http://www.HollowayDiamonds.com.au |
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maybe this has been answered some place else, if so, sorry. but,
with the new GIA "facetware" program, it calls for some measurements that I am unfamiliar with. Star % and lower half %. I *think i know what they are in general referring to, but just to be sure, can somebody explain it? Also, is there any way to obtain this information at all? probably not without having it measured eh? also, how on an old GIA report would one obtain the girdle %, If it just says "medium" or "medium to sl. thick" man, that is a lot of rounding... |
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Lower girdle: http://www.octonus.ru/oct/products/helium/polish/parameter05.phtml Star ratio is the same thing measured as a % from top down on minor crown facets. Girdle thickness for GIA depends on diameter - Do a googlke search on Martin Haske SAS and girdle thickness - you will find the info you need - But GIA now use the thickest part - not the thin valley - so Medium is around 3% for 1ct i think
Garry Holloway FGAA DipDT
HCA and Ideal-scope developer http://www.ideal-scope.com and http://www.HollowayDiamonds.com.au |
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Thanks!
A word of caution to others who may be "googling" if you type in "Martin Haske SAS and girdle thickness" without any quotes, you will obtain numerous results you probably won''t want to click on, especially if you are at work! probably a better idea to type in "Martin Haske" "girdle thickness" it gives better results! |
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yikes!  hope you found the information you were looking for sylvesterii.
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Intervals in Facetware for Lower Half Length & Star Length are 5% so the different methods of measuring shouldn''t effect the end result too much.
Here''s a link to tha Rap article explaing the measurments and tolerances. http://www.diamondcut.gia.edu/pdf/0805_pg34_39.pdf |
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Garry,
You are usually right on top of cut issues, so I am curious why you made this seemingly incorrect statement: "Girdle thickness for GIA depends on diameter - But GIA now use the thickest part - not the thin valley" Garry Holloway At http://www.diamondcut.gia.edu/05_diamond_anatomy.html , under Girdle Thickness, GIA says: "Described and reported by the GIA Laboratory as a range from the thinnest to the thickest "valley" areas (i.e., "thin places" located between the bezel-main intersection and where the upper and lower halves meet)." The latest Rappaport News at: http://www.diamonds.net/news/newsitem.asp?num=14040&type=all&topic=all has an article "Culet and Girdle Assessment" that says: "It is important to note that there will be no change in the GIA Laboratory’s methods for assessing culet size and girdle thickness due to the introduction of the new cut grading system." "Girdle thickness is assessed as a range from the thinnest to thickest “valley” positions; these “valley” positions – or “thin areas” – are located where the upper and lower half facets come closest to meeting" "Graders visually assess girdle thickness at 10X magnification with the diamond in profile view and consider each of the 16 “valley” positions and their thicknesses relative to the diameter of the diamond." What''s the story? Am I missing something? Michael Cowing www.acagemlab.com |
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it is rather interesting isn''t it Michael (
 New Year BTW).The GIA Facetware site inputs and outputs girdle measurements at the thick part. As Marty has shown - their grading method is to assess (which seems to get the same result as measurement) girdle at the thin part. A slightly thick 10ct diamond has a girdle thickness that AGS would grade as thin or very thin. No reason for GIA to change this - it makes sense - but in all the Sarin Facetware etc - the cut grade stuff seems to be at the mains thick part. AGS btw are reporting the thinnest valley to the thicketst mains - this looks weird on their reports. eg 0.7% to 4.0% - still gets AGS 0.
Garry Holloway FGAA DipDT
HCA and Ideal-scope developer http://www.ideal-scope.com and http://www.HollowayDiamonds.com.au |
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Hi Garry,
Happy New year to you and all the pricescope family. Regarding: The GIA Facetware site inputs and outputs girdle measurements at the thick part. Their grading method is to assess the girdle at the thin part. A slightly thick 10ct diamond has a girdle thickness that AGS would grade as thin or very thin. No reason for GIA to change this - it makes sense - but in all the Sarin Facetware etc - the cut grade stuff seems to be at the mains thick part. AGS btw are reporting the thinnest valley to the thicketst mains - this looks weird on their reports. eg 0.7% to 4.0% - still gets AGS 0. <<<<<<<<<<<<<<<<<<>>>>>>>>>>>>>>>>>>> This is confusing. My understanding accords with GIA''s statement: "It is important to note that there will be no change in the GIA Laboratory’s methods for assessing culet size and girdle thickness due to the introduction of the new cut grading system." So my current belief is that the Facetware input of thin, medium, thick etc. is still based upon evaluation at the valleys in the usual manner. I see logic in the AGS reporting the complete range of girdle thickness from valleys to peaks. At a glance, you observe the thinnest valley and the thickness at the mains, so you know if the girdle gets perilously thin anywhere. And you have the thickness at the mains, which when added to the crown height and pavilion depth should accord well with the total depth. I also think there is merit in AGS having a % based girdle thickness, which allows for the same % girdle thickness in a larger diamond as it does, for example, in the one carat. Haske''s analysis appeared to show that GIA girdle thickness grades are not proportional to the diamond diameter as they are in the AGS percentage based grades. We should get some clarification of all this from both GIA and AGS. Michael Cowing www.acagemlab.com |
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You have seen that the www.facetware.gia.edu site uses % at the mains Michael?
And all the reporting in G&G Fall 2004 and 2002 is on mains thickness.
Garry Holloway FGAA DipDT
HCA and Ideal-scope developer http://www.ideal-scope.com and http://www.HollowayDiamonds.com.au |