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Gia Grading


momof3
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Just purchased a 1.72 diamond. It is just barely a GIA excellent cut and also is excellent symmetry and polish. Has anyone had a stone similar to these dimensions (off the report)

 

1.72 ct

table 60%

depth 59.5%

crown angle 31.5 degrees

pavillion angle 41.6 degrees

thin - med faceted 3% girdle

 

I am reading on another site that some don't recommend these measurements of the crown & pavillion although it is graded excellent for cut. Feedback appreciated!

Edited by momof3
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GIA cover a lot of ground with their "Excellent" and "Very Good" cut grades. On the one hand, it is good because it allows for significantly different appearances to be classed as "EX" or "VG", and at the end of the day personal aesthetic preferences are a significant factor in judging excellence. On the other, it leaves the door open for stones that I would call "acceptable" but certainly not "excellent" to end up in its top category.

 

I have (or rather, my wife has) a step-cut that probably looks similar to your round: shallow crown and wide table. She loves it, and so do most people that see it in photo or in real life. It's a very bright stone, with lovely contrast and sparkle, but lacks (in my opinion) fire. Is it "the best"? Not by any means, but it's very good at doing what it does - I wanted a "black and white" look to contrast with the pink sides.

 

Pink5.jpg

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Hi Mom;

 

Light refraction and hence the face up look of the diamond; it's brilliance, dispersion, scintillation, and contrast brilliance is affected by the combination of the crown, pavilion, table facets as well as the upper and lower half girdle facets.

 

Preference is personal and subjective and probably the best way for you to determine your preference is to compare the diamond you've purchased against a diamond with specs recommended on the Internet site you canvassed. Then see which you prefer.

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What they’re not liking is that the pavilion angles are a little high for the optimum light return and the crown is a little high in relationship to the pavilion for maximum internal reflection. In both cases it’s near the boundary of what most people would call optimum and the tradeoff is usually in the weight and the price. This can easily be offset by personal taste as mentioned above. ‘Light return’ for example, is on the other side of contrast, which is itself a part of scintillation. This is the attribute of diamonds to show ‘life’ when you move the stone, the viewer or the light. It’s part of what makes them cool. You CANâ€T maximize both of these things at the same time and it’s a balancing act to decide what is the best mix. It’s wickedly difficult to do this based on a set of averaged numbers and it’s the reason GIA-excellent is so broad (well, it’s one of the reasons, industry pressure played a big part in this decision). I have some issues with GIA but, in this case, I agree with them. Having taste that’s a bit outside of the middle of what someone calls ‘best’, is not the same as being wrong. Otherwise excellent stones that get slammed as 'steep/deep' usually seem to be high contrast and high scintillation.

Edited by denverappraiser
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Thanks for the replies! There were no other stones in diamond search that had these crown & pav angles. My daughter wanted a "spready" stone. Locals said a 59-60% table was what she needed to look for. Only after the purchase did she & I educate ourselves about the tools to buy a diamond such as HCA which in itself is confusing. I get two different scores depending on whether I use angle degrees or percentages. Reading that rounding off is used by GIA which makes me question what the actual angle degrees are. Did they round favorably to get the EX cut grade or less fav which still might have the ex cut grade but might impact the HCA grade. The jeweler in question is a recommended vendor in NY. He has looked at it , says it is eye clean facing up whiter than the " I "color it is, says his "cutter/supplier" states it is a clean clear stone with alot of bite?? What is that? Well she has 30 days to decide. It will be placed in an 18kWG setting with side stones. I hope she understands spreadiness might mean sacrificing scintillation. Anymore feedback always much appreciated.

Edited by momof3
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With the HCA the recommendation by its inventor is to use degrees. Again, the HCA is a reject tool not a pick tool and uses rounded off numbers to evaluate 17 of the 58 facets that comprise the round shape. We have evaluated and recommended many diamonds that have scored above 2.0.

 

Use your 30 day return period to perhaps compare to other diamonds that have different "numbers".

Edited by barry
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GIA will round to the nearest (0.2° for pavilion, 0.5° for crown), regardless of whether this will result in a lower or higher cut grade.

 

You are way beyond the point at which the HCA may be helpful - it's meant to help you come down with a shortlist, not decide whether the diamond you see is "better" than another one: your eyes can do that much more easily. As Barry said, talk to your vendor, ask if they have something that is closer to "classical" proportions, and see if you and your daughter like it better.

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HI,

To make life easier, if GIA graded the stone with 3 X EX, the stones has perfect proportions.

Meaning that the light going through this stone will deliver the perfect shine.

All the small details are not important, they may be important between dealers, looking for a way to negotiate prices on perfect stones.

 

 

 

 

DAN GILDONI CEO,

WWW.DIAMONDFLOOR.COM

 

+972 3 613 8780 (Office)

+852 3678 6715 (Hong Kong)

+1 212 874 3634 (New York)

dan@diamondfloor.com

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Hi Dan,

 

I absolutely disagree. I would never use the phrase perfect anyway but what's important is whatever the buyer thinks is important. It's their money and if they're interested in something else (like hearts and arrows symmetryor 'fair trade' for example) it's thier choice.

 

GIA-excellent is a very broad brush and it is NOT the end all for cutting questions. It's rather like taking a pass/fail class in school and saying that 'Pass' is the same as 'A+'. It might be, but it might not.

Edited by denverappraiser
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I guess when the stone actually arrives I will have alot of my concerns answered. Hoping for a sparkly white stone with good spread :) I will go and compare but I doubt I will find that spready of a stone to compare it with since the diameters of this 1.72 stone make it face up almost 2 carats. I guess I could compare it to a 2 carat with "ideal" HCA proportions but then it goes back to price and if the stone is "gorgeous" to the average every day person that would look at it with nothing close to it to compare. I would certainly hope GIA would not give a dead looking stone with no sparkle/scintillation a triple ex. From what I understand GIA has three sets of eyes look at the stone and all give it a color grade and cut grade and the average of the three is what they go with.

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The GIA cut grade is assigned purely by computer and then humans have the opportunity to downgrade it based on the symmetry and polish observations. The humans do NOT have the opportunity to upgrade from what the computer assigns beyond redoing the scan to correct errors..

 

That said, I agree that it's almost certainly a lovely stone that nicely meets your requirements. Congratulations. Ignore the HCA entirely.

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Just for clarity purposes, that info didn't come from AGS, it came from the dealer using a tool that came from Sarin and software from AGS and Octonus. I don't have a problem with any of that but don't confuse it with an inspection by AGS lab.

 

In one of the reports you posted, the dealer gave it symmetry and polish grades of '4'. This is a bit surprising given the GIA report calling these 'excellent'. It may just be a typo but ask them what's up with that.

Edited by denverappraiser
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Hi actually I called AGS and spoke to

Patrick B. Stout

Certified Gemologist Appraiser

Education Services Manager

Tel: 702-255-6500 ext. 1020

Fax: 702-255-7420

Toll Free: 866-805-6500 ext. 1020

 

He explained what he was doing in great detail and claimed he gave a 4 as a default since polish & symmetry aren't really gauged?? Can I send you all of what he sent to me (entire report & explanation) Can I send it to your e-mail Neil?

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Patrick is definitely an AGS guy and he ran the AGS software using a sarin file that was taken somewhere else. I'll be happy to take a look but be aware that I charge for this sort of work.

 

Sarin does not measure polish or symmetry and the AGS software doesn't evaluate anything beyond what it's told. P&S are data entered by the gemologist using the software (in this case Patrick), based on their physical observations. Given he hasn't seen the stone, he's guessing.

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To a consumer it is so frustrating :wacko: . I assumed he would know the definitive answer being from AGS. He used the sarin file received from the jeweler and also ran another test to make sure the sarin file was for the stone in question and the angles etc matched up. I asked would he buy it and his comment was it is a fabulous stone @@ I asked why and he said it would have lots of sparkle and be very bright. Now" G. H". also commented on another site and basically felt this guy was all wrong. AGS claimed with the sarin file it was like having the diamond there because it computes how the light will impact the diamond based on alot of info input into the software program AGS has on site. I was surprised he did it for free but i think he heard the concern in my voice and was just being very nice/or was bored that day lol. I wanted to basically send you all his comments concerning the stone because he used words like "extremely rare" etc which can be misleading. Sending you the e-mail was not for an appraisal more or less just what you make of his observations.I can post the actual e-mail here but it is long and I wasn't sure it was allowed? I already posted the graphics from the e-mail so it would be his "take" on what the program indicated. In a few weeks I will get to see it in person!

BTW Thanks Neil for following this thread and responding!

 

 

:ph34r:

Edited by momof3
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Sarin makes good equipment but no piece of software can evaluate more than what it has to work with in terms of data. In the case of Sarin files, this includes things like the callibration of the individual machine that did the scan and even things like dust on the stone. Things that aren't scanned, like color, clarity, polish and symmetry are obviously off the table for this sort of evaluation.

 

I suspect he's right, it's surely a lovely stone but bear in mind, Patrick works for AGS, and AGS is a network of jewelry stores. Part of his job is to help his clients to sell diamonds. Like me, he has never seen it.

Edited by denverappraiser
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  • 3 weeks later...

Getting nervous! The stone should be here before the 10th. I guess the holidays slowed things down as i thought I would have it by now! It was sent to Precision set from Since1910.com for them to set it so a week added. If i haven't elaborated why I am so nervous it is because I have helped my son in law to be to pick out a stone for my daughter. I know she wants a spready stone so this fit what she wanted. I wish I had found all the tools prior to ordering it like HCA. Anyway as soon as I get it I will post pics taken in several lighting stituations. I know my SIL to be will send it back if not pretty but prices have gone up. The stone was 13,300 less 5% discount and if he had to find another he is looking at spending at least 2,000 more then early Nov prices!

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