I noticed some stones on the (lab-created) price tracker are denoted as “Ideal Proportions” but when I look at the lab report they fall outside both GIA EX/AGS 0.
An example is James Allen SKU:7203029. The IGI report says table 58%, crown 34.9, pavillion 40.2. When I plug that into the cut estimator it falls in GIA VG/AGS VG.
In fact, not a single IGI report I’ve requested for lab grown diamonds fall in either GIA EX/AGS 0. Am I doing something wrong?!
Thank you for your observations. It identifies the limits of machine learning.
For James Allen, I evaluate cut quality and optical symmetry using computer vision to look for 8 crisp arrows (https://www.diamondscreener.com/education/evaluating-round-diamond-cut-quality-using-computer-vision/). My vision-based classifier was trained on natural EX diamonds, the vast majority of which were graded by GIA. GIA EX does not include the proportions of the example diamond you gave, so why I apply my classifier to GIA EX diamonds, such a diamond would never appear.
For lab diamonds, the vast majority are graded by IGI and IGI’s EX grade can include a diamond with a pavilion angle of 40.2. However, my computer vision algorithm still sees that it has 8 strong arrows, which you can confirm in the images. I think 7203029 has nice optical symmetry, so then it’s a question of whether to go by the paper or by what you see.
Interestingly, in the IGI subset of my natural diamond training set, only about 30% of the IGI diamonds that my vision classifier said had ideal proporitons had a pavilion angle < 40.6. I would have guessed that percentage would carry over to the lab diamonds (unless natural and lab IGI diamonds don’t follow the same prior distribution). How many diamonds have you requested the IGI lab reports for? I’m a bit surprised that zero of them qualified.
I just pushed out a new update to the code that increases the score cutoff threshold to try to boost the sensitivity. Maybe give that a try?
I enjoyed digging into this issue.