New GIA cut-grading-system launch Jan 2006
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Yes, Paul thanks.
Questions and observations... How cool is this announcement to you professionals of the trade? Largely consistent with what had been expected? I''d heard John poking fun/irritation at the anticipation 5% variation for minor facets. I see what seems odd as not only a .2% variation for pavilion angle, but a commitment to keep it''s validity somewhat obscured, by the promise of it only being reported on even numbers. Why not accept odd numbers and then presume .2% variation? A minor point? Re tools, where does the diamond dock fit into what GIA is offering for the trade to help? Regards, |
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Basically, there is nothing that I am surprised about. The fact of rounding was sufficiently announced before, and I have reported about that quite often.
I am amazed that they are really going to introduce it. I expected them to postpone it again and again, until they would shelve the whole issue. In my eyes, the whole system is a farce. If I see that a 60% table with 41.8° pavilion angle, 33° crown angle and 80% lower girdles and 50% star size scores Excellent, that is horrific. The same combination, if cut extremely symmetrically, would score AGS-5 at best in the new AGS-system. The result will be that the majority (after some adaptation, I expect at least 80%) of the rounds graded by GIA, will get an Excellent cut-grade. What is the use of all this then? Live long, |
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As much as we gemologists love and respect the GIA for what it has been able to accomplish over the past 60 years, one is left wondering how their "new" strategy for grading cut is going to advance the science or accuracy of graders and appraisers. I have openly been admitting for a number of years that grading by parameters is a useful screening tool, but not the final answer on how well a diamond performs. I should know, since I have been attempting to grade by parameter since before anyone seemed to care about it at all....since around 1986.
When we put "Tolkowsky" cut parameter stones, or current AGS 0 round diamonds on the ImaGem machine we don't get consistent results because cutters have figured out how to squeeze a little more weight into the finished stone and sometimes this hurts light performance. The parameters look quite good, but the stone isn't so hot. Now, the GIA proposes to measure a few more angles and facet lengths, but seems to be still stuck on looking out for "pasting" and "digging" of certain facets which will have a definite effect on final light quality. I think the proposed system has benefits for cutters, but may be leaving many loopholes that will not serve consumers well. A lot of not so fine diamonds will grade "excellent". How will one select the best one if they all grade the same? It needs more discrimination. You can measure until the end of time, but there is always another variable. If you take care of round diamonds, how on earth will you be able to measure they myriad variables of fancy shapes. I think direct measurement of light performance will outshine, pun intended, any attempt to quantify beauty by looking at parameters. There are simply too many variables and when added to the inherent inaccuracy of the measuring devices they propose to use, it makes the final resultant "cut grade" doubtful. I am trying very hard to play nice! I note Paul and I were writing our responses at the same time...We seem to be saying just about the same things, too. David S. Atlas, GG(GIA) Sr Mbr(NAJA) ASG(AGA) My basket of services available to Pricescopers |
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I dunno, seems rather encouraging to me....at least from the point of view of being a consumer.
I think it''s very important to separate a) reporting from b) analysis. Dave, although you say...
Maybe rounds are straightforward enough. So what if GIA has what''s regarded as substandard analysis, for reasons of political correctness, or otherwise. If a map maker were precise in their measurements, showing where different streets were located in a country, if they make the mistake of calling each and every destination New York City, a smarter interpreter could come in, look at their data, and provide new names for the different places, without having to re-collect the data. Now, for some of you smart experts, here''s a question... which would you rather have, presuming you could not do your own measuring, independent of what you are given. A map with measurements including crown & pavilion data, and a general light performance grade or a map with crown & pavilion data, along with minor facet info. For skilled appraisers, who do not have proportion measuring equipment, and when presented with options to consider from their customer...isn''t that exactly what they are facing? Excluding what they may do well not to exclude...which is the diamonholder''s intention when having sent the diamond to AGS...which set of data would you prefer to have? Isn''t that how smart diamond shoppers will be viewing their options circa January 2006? |
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maxine, the answer to that would be no. 
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I''ve been playing with the software a bit today. Gosh is your conclusion an understatement. I have some interesting examples to post tomorrow. |
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I also played with some stones today. Lots of excellent, nothing below very good. The old AGS scale had them ranging from 0 to 7. Hmmm.
I think we are going to see cutters using a 4 step cut grading scale: AGS - 0 - For stones that can get it GIA Excellent - Most stones GIA Very Good - Stones that the cutter thought would get excellent but didnt for some reason. GIA Poor to Good & AGS 2-10 - Stones waiting to be sent to EGL for regrading This is not very different from the system that''s been in place for years. AGS-0 - for stones that can get it AGS-1 for stones with AGS-0 proportions as determined by a Sarin but that failed for symmetry or polish GIA with Sarin sticker for stones that are pretty nice GIA with no Sarin Sticker for stones that are nice but where the sticker says too much EGL - all others I suspect that this is not as revolutionary a change as the labs would have us believe. Neil Beaty GG(GIA) ISA NAJA Independent Appraisals in Denver |
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Claps, not slaps, Wink... Reese Witherspoon would say ‘snaps for Wink’. At a glance, here are a few examples from GIA of proportions sets that would qualify for their ‘Excellent’ and 'Good' grades (the EX sets are not particularly heinous in any way...there is even a nice 61% table in there for David). Excellent cut grade candidates Linked here. Good cut grade candidates Linked here. (source) I can’t believe that proportions-based grading will be as meaningful as assessment of the actual diamond of the kind that AGS has evolved to. It is like comparing HCA to ideal-scope - you WANT both sets of info, but the light performance image trumps the measurements descriptions. Where AGS will be providing both measurements and ASET evaluation, GIA has no plans to include light performance. In some ways GIA seems to be starting where AGS was in 1996, with a softer range for their top grade. For newcomers, Garry H. did a review of GIA test subject diamonds in his review of the foundation of the forthcoming system linked here. |
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hca for that combo:
Selected: 60% depth, 56% table, 34.5° crown angle, 40.8° pavilion angle The result is for a symmetrical diamond with a medium girdle and very good polish HCA scores were adjusted Dec. 15, 2001 and Feb. 6, 2003. Factor Grade Light Return Excellent Fire Excellent Scintillation Excellent Spread or diameter for weight Excellent Total Visual Performance 1.1 - Excellent within TIC range |
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strmrdr well....if that''s true,we can for the new reports to come out and buy some cheap GIA stones with those proportions.  so,even with the new report, we still need a sarin scan b/c of all these round off to the nearest what ever. 
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I can appreciate that for those of you experts here, the story is about the analysis. And, so it should be.
But, I still say that the story about the Gutenberg Bible is not about the Bible story...it''s about the fact that presses were used. As Neil says:
The revolution is in the documenting of the data. As is noted in the tutorial, 73% of diamonds are provided with docs from GIA. Presuming this doesn''t change substantially, these 73% will now have data regarding their cut, it will impact all the diamonds in the quick search...and with details on minor facets that are not provided on AGS certs. Surely, this should motivate more attention to this sort of info, and of course, that has been reviewed here before as well. To Dancing Fire...though it seems reasonable to me that more attention could be given to this ("we still need a sarin scan b/c of all these round off to the nearest what ever"), I''ll bet that except for certain combinations, the detail provided will be regarded as helpful enough to specify. And to Maxine...I think the main logic is really reversed on this ("So, now will all appraisers have to have the sarin or comparable machine to be able to measure the diamond and verify the grade???"). Right now, while GIA until January includes no cut data, although most appraisers could be providing a unique and needed service, of providing this data... they don''t. Come January, if they start to do this as a result of GIA''s new published interest, I for one could care less. As is the case even now with appraisers who review diamonds with docs from AGS...if they have sarin and make measures that diverge from AGS, the general presumption of accuracy is with AGS...and so it would almost certainly be with GIA, as well. So, though the story is boring here, because the vendors here will routinely provide this data on their in-house options...that big database supposedly has 50,000 diamonds. That''s a lot of info to be able to cull through. Isn''t that the story? Regards, |
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Same here for internet stones. However for a stone im seeing in person an ags report with angles, ideal-scope and h&a scope and a microscope/loupe would be enough. The rest of the reports would be icing on the cake. |
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I can honestly say I wish I didn''t read this thread.
I am so close to purchasing a GIA EX, EX diamond with proportions that score under 2 on the HCA. These proportions are similar to those listed above. I am sure my diamond is a performer, but of course having not seen it yet, it creates one more thing to question. Of course the scientist side of me wants to investigate further. Most lilely after the purchase. 
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Ira, This will indeed be the issue and there’s a huge pile of money on the table. Very soon, a stone graded by GIA before 1/1/2006 will be viewed as automatically inferior, and consequently less expensive than a stone with a new report. This means that the owners of 73% of those 50,000 stones will need to make a decision. They will be required to resubmit the stone for a new examination (and pay the fee) or tolerate a lower selling price. This is not a decision to make lightly and it’s not a position that they are happy about being forced into. Those things are expensive and we are talking about millions of dollars in lab fees just to bring existing inventory up to current standards. A report with a GIA ‘fair’ or ‘poor’ cut grade is going to be worse than no report at all and the dealers will respond to this by either selling the stone without a lab report or by choosing a lab that doesn’t include this information. I think the same thing is going to happen on the high end. If they have to resubmit a stone and they have the option of AGS-0 or GIA-excellent, I think a growing percentage will choose AGS because the selling premium will be higher. If I could do it, I would be buying stock in AGS Lab, EGL and Imagem right now and I’ld be short selling GIA. It’s sort of a shame that none of these are public companies so we could watch the fireworks. As with most things, the real battle will be over the middle ground. Other things being equal, is a GIA-excellent better (meaning more saleable) than an AGS-3? How about a GIA-good vs. an EGL-nothing? What about Imagem and the other labs that barely make the radar right now? I don’t know but this is the competitive area for the labs. More and more customers are demanding lab services and the while the percentage of stones accompanied by a report is increasing, the percentage those reports that are issued by GIA is going down. I think this is a big part of the reason that GIA is being so slow to introduce the new system. It’s almost impossible for them to win. If the category of ‘excellent’ is to narrow, their customers will flee to AGS and if it’s too broad the consumers will consider it useless. The best option is to drag their feet as long as possible. Does anyone know if the diamond dossier reports will also include the cut grade? Neil Beaty GG(GIA) ISA NAJA Independent Appraisals in Denver |
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The proportions are cherry Im either missing something or the GIA software or the grading criteria are out of wack. Something strange is going on. It is way too early to hit the panic mode on this. |
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Hey Storm, I suppose that you left the total depth at 60%. It took me about four double-clicks, but then, you can adjust the total depth. From 60.6% and higher, this proportion-set will be Excellent. Live long, |
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Your right. I tried about a dozen times to change the depth and it wouldnt budge. But at 60% depth why are they knocking it down? According to diamcalc its no problem? |
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This is very interesting Paul. Funny but when I do my searches I punch in depths that range from 60.6 - 62.2%. |
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Looks like it may be knocking it down for too thin a girdle at 60% atleast thats the only reason I can see. |
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Strm... for your info the lower girdle measurements given within Diamcalc are not the same that GIA is looking at.
GIA/Sarin measure lower girdle length. This measurement is taken along the horizontal plane from girdle to culet and comparing the lower girdle length in relation along the horizontal plane. AGS/Helium measure lower girdle height. This measurement is taken along the vertical plane comparing the height/depth of the lower girdles in relation to pavilion depth. Note: Helium actually gives both measurements (lg height and length, along both planes). Here is the conversion chart for determining lower girdle length if you're using DiamCalc. So ... an 80% lower girdle length (length needed for new GIA Cut Calculater) would translate to 81.5% lg height in DiamCalc.
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Ok... playing around today a lil with the new GIA Cut Calculator. I''m finding many positives and also some negatives. One that is really throwing me for a loop is this ...
Here are known poop proportions for an ideal cut and the stone DOES NOT get a GIA Grade 1. Hooray for GIA!
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