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Does this diamond shows that AGS cut grading is unreliable?

G

gcsw

Rough_Rock
Joined
Jul 9, 2017
Messages
5
I was looking for some honest feedback. I have some concerns about this diamond as I already put a 20% deposit down and it's non refundable.

When looking at the AGS Round Brilliant Guidelines Chart, the angle combination of crown/pavilion of 33.3/40.7 for a 57% table falls somewhere between Very Good to Excellent rather than Ideal cut. But AGS had it graded as an Ideal cut. 1.017 carat. The most important C for me was the cut as i was really looking for something brilliant and scintillating. This diamond is also supposed to be Hearts and Arrow, and eye clean.

What are your thoughts? Is it a poorly cut diamond?

https://www.americangemsociety.org/Content/uploads/6mm-57Guidelines.pdf

AGS ideal.png
 
There is AGS grading based off proportions and then there is AGS cut grading which takes into account light performance using ray tracing etc. This stone looks like it's been graded using the latter option as it appears to have a Platinum Light Performance report. Agreed though, the CA/PA combo is not what most of us here would usually suggest though the extract of the report with the computer generated ASET looks good to my eyes.
 
Why did you put down a non-refundable deposit if you had concerns?
 
Because I didn't realize the proportions didn't fit the Ideal proportion guidelines until after the fact.

Bmfang, is there one method that would be considered more 'reliable' to assessing the cut (brilliance, scintillation, fire, sparkle, etc) ? Is it ray tracing or proportions/numbers?

Could this mean that this is a lower end of an AGS ideal cut?
 
This report is the modern light performance based report. It's much more sophisticated than a table-based report based solely on rounded averaged proportions. The diamond has been thoroughly ray traced and verified to have no significant deficits in brightness, leakage, contrast or dispersion (fire). And the ASET light map indicates a high level of optical symmetry as well. It may not be in the sweet spot of AGS Ideal, but that is a very high standard to begin with.
 
First, I think the diamond is fine. The crown is a bit low and there is likely some deduction in dispersion (affecting fire/sparkle), but nothing alarming.

Speaking of AGS light performance grading based on ray-tracing in general, iit is not 100% reliable (no grade system is), and there are some real duds among AGS 000.

eg..
https://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3859293.htm?source=pricescope
(note: the stone has nothing to do with WF. it is from virtual inventory)
 
For future reference, NEVER buy a diamond from a seller asking for a non-refundable deposit. That is a red flag right there. Vendors here have from 10 to 30 day full refund periods. You need to have the right to return, period. Fortunately the diamond looks okay, but I worry about the integrity of vendors who do that.
 
Ok, thanks everyone for your input which was very helpful for my own peace of mind. I was worried that i was paying a premium unnecessarily for an Ideal graded diamond when its light performance/cut is closer to an Excellent/Very Good one. I was looking for a stone that would have as much sparkle as possible.
@flyingpig i would imagine that the deduction in dispersion you mentioned affecting fire/sparkle won't really be visible to the naked eye compared to a stone with the favored crown angle of 34-35?
 
gcsw said:
Ok, thanks everyone for your input which was very helpful for my own peace of mind. I was worried that i was paying a premium unnecessarily for an Ideal graded diamond when its light performance/cut is closer to an Excellent/Very Good one. I was looking for a stone that would have as much sparkle as possible.
@flyingpig i would imagine that the deduction in dispersion you mentioned affecting fire/sparkle won't really be visible to the naked eye compared to a stone with the favored crown angle of 34-35?
Click to expand...
At this level of cut quality, the clarity features in this diamond would be more likely to have a visual impact on fire/sparkle than any small deduction for dispersion due to crown angle.
 
Texas Leaguer said:
At this level of cut quality, the clarity features in this diamond would be more likely to have a visual impact on fire/sparkle than any small deduction for dispersion due to crown angle.
Click to expand...

Does that mean it's not exactly an eye clean diamond? Is it the cloud or crystals in table that is the issue?
 
He can't tell you if it's eyeclean without seeing it. But I assume he was referring to the clouds, shown and not shown, on the report.
 
Yes, DS is correct. I was trying to put in perspective your concern about small cutting technicalities that may place the stone outside the 'bullseye' of AGS Ideal. In Si clarities, characteristics with light scattering properties have the potential to diminish overall light performance. It's impossible to say from the data on this cert whether the stone is eye-clean or whether the clouds have any impact on transparency. Having an qualified independent expert examine the stone with you is always a very good idea. Any deficits due to clarity characteristics are likely to be very subtle. But they won't be the result of cut quality on this stone.
 
If an SI1 diamond is considered eye clean, is it still possible for the inclusions to diminish the overall light performance, at least in theory?

This is a picture of the diamond.

diamond image.jpg
 
Yes, it is possible. Particularly when the clarity grade is based on clouds or other light scattering type inclusions. In this case the grade setting inclusion type is crystal (listed first under key) so there is less of a chance of haziness. The cloud plotted is not much of a concern, but there is mention in comments of clouds not shown. The impact of those is unknown until you have the stone examined. The image looks a little hazy, but it also does not seem to be in focus, so nothing really can be learned from the photo in terms of transparency.
 
gcsw said:
If an SI1 diamond is considered eye clean, is it still possible for the inclusions to diminish the overall light performance, at least in theory?diamond image.jpg
Click to expand...
Edited to add: Stepped away before posting and Bryan beat me to it (Hi Bryan).

Yes, but usually the grade-setting feature will be clouds, pinpoints or graining.

The diamond in the top post has an SI1 grade based on its crystals. The plotted cloud was considered secondary and those "not shown" were considered non-factors.

Moving away from this example to fully answer your question: Yes, but every diamond is different. Among those I mentioned in the first sentence that could be diminished; some examples have no issues whatsoever. Some are not detected unless subjected to some level of scrutiny. Other have notably muted optics (aka "sleepy" diamonds).
 
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