Often, GIA triple excellent diamonds may not fall under strict proportional criteria for Table, angles, etc, and I’ve really enjoyed using diamondscreener to compare proportions. As has been mentioned, many GIA triple excellent diamonds might fall at an intersection with the ideal AGS / GIA excellent tool areas.
Some diamonds might fall in the ideal areas on the tool, but have proportions outside of the very strict criteria proposed by many sources (such as Beyond4cs)
Table: 54 – 57
Depth: 61 – 62.5
Crown Angle: 34-35
Pavilion Angle: 40.6 – 40.1
I’d like to illustrate some examples and solicit opinions! Here are the diamonds of interest:
Diamond #1 Diamond #2Diamond #3Diamond #4Price$11,261$11,212$11,455$13,680Carat Weight111.041.01ShapeRDRDRDRDCutIdealIdealIdealIdealColorFFGFClarityVS1VS1VS1VVS1L/W Ratio1.010.9911Depth %62.361.761.862Table %55575656Crown Angle3633.534.534.5Pavillion40.641.240.840.8GIA/AGS Intersect?No (intersect)YesYesYesPolishExcellentExcellentExcellentExcellentSymmetryExcellentExcellentExcellentExcellentCuletNoneNoneNoneNoneFluorescenceNoneNoneNoneNoneInclusionsTop: small featherTop: small Crystal, needleTop: crystal, cloudTop: noneBottom: pinpointsBottom: n/a bottom: pinpoint, feather
For example – Diamond #1 – Meets Beyond4Cs’ strict criteria, but only borderline in the tool:
Next example: Diamond #2 – Does not meet Beyond4C criteria, but is in the sweet spot:
Diamonds 3 and 4 are added for comparison as they meet both Beyond4C’s criteria and hit the sweet spot, at the expense of color or price.
As an online shopper (using a site that doesn’t offer in-person viewing of stones) – is it better for light performance to prioritize strict proportions such as those outlined by Beyond4C (Diamonds 1 – not in sweet spot, 3, 4)? Or, if hitting the AGS/GIA sweet spot in the tool (as above, Diamond #2), are more relaxed proportions acceptable?
I realize Cut > Color > Clarity, so really curious how you all would interpret the tool and evaluate these diamonds. Thanks for reading!
I wouldn’t say the proportion-based criteria create a “sweet spot” per se. Ideal proportions are necessary, but not sufficient, for nice optical symmetry. Although a diamond might be GIA EX/AGS 0 Ideal, it’s generally harder to find nice optical symmetry with pavilion angles > 41, as shown in my computer vision analyses.
Something like dIamond 1 (36 crown angle/40.6 pavilion angle) doesn’t fit the tight criteria you’ve defined because the 36 pavilion angle is outside of the 34-35 range. However, the 36/40.6 combination generally shows nice optical symmetry – optical symmetry is more sensitive to the pavilion angle than the crown angle. It’s GIA EX/AGS 0 Ideal – I wouldn’t make further distinctions within that category if it shows nice optical symmetry.
In contrast something like diamond 2 (33.5 crown angle/41.2 pavilion angle) generally has a harder time showing all 8 arrows. Both of these observations can be checked from the examples shown in the cut estimator.
So in this case, based on the proportions, I would guess that diamond 1 looks better than diamond 2. However, you’d need videos to check this and also to evaluate the inclusions. Similarly, just because diamonds 3 and 4 have nice proportions doesn’t imply they have nice optical symmetry. You’d also want to check their videos for optical symmetry and inclusions. If diamond 1 and diamond 3/4 all have similar appearance and the inclusions are fine, then I would go with the cheapest one.
In summary, I don’t think it’s necessary to prioritize strict inclusions. There’s certainly more wiggle room on the crown angle side to show nice optical symmetry, and many of those options will save you money.