Accuracy of HCA Rating

the HCA is one tool that can be used in evaluating diamonds...AGS cut grades are another. since JA is selling that as one of their true hearts stones they should post an idealscope image. They will review 3 diamonds for you so perhaps find 2 others to compare?

AGS trumps because they evaluate the actual stone in person not just a few of the angles virtually like the HCA. If it's an AGS 0 certificate the HCA doesn't really matter. But I would get an IS image.

Thank you! I have emailed and asked for an Idealscope of both stones.

I totally agree. You don't even enter AGS0 stones in the HCA because it is unnecessary. I wouldn't really even have to have an idealscope on an AGS0 stone.

Written by diamondseeker2006:I totally agree. You don't even enter AGS0 stones in the HCA because it is unnecessary. I wouldn't really even have to have an idealscope on an AGS0 stone.

Yea- AGS seems to be the strictest in terms of grading cut

It is my belief that AGS grades the cut based on their research of how various parameters of diamond measurements interact to create light return and not by measuring the actual light return from an individual diamond. An AGS ASET image can be the actual diamond being graded or a virtual image based on DiamCalc or proprietary software driven by Sarin, or other scanner, measurements. The assumption is that the diamond is unaffected by any clarity or transparency issue(s). This can throw a curve into AGS0 or HCA predictive grading.

I have not seen a single AGS0 diamond which I felt had some visual issue because the care involved in cutting to those specs precludes most cutters from taking the time to cut a diamond which had visual problems, but it is a possibility.

An HCA rating is a decent pre-screening predictor of light return, but it sure is not a 100% cure. AGS0 is an excellent predictor of high end light return, but it needs to be understood that not all AGS0 diamonds are cookie cutter similar of one another. There remain variations within the grade.

The correct way to grade light return and its associated characteristics is by direct measurement of the light return itself. Every other method done by prediction has flaws that may show up on occasion. While one may believe that maximizing light return is the key to a beautiful diamond and also a top cut grade diamond, there likely is evidence that maximization is not necessarily the key ingredient. A diamond needs a particular "look" created by brightness and contrasting darkness. It appears that humans prefer a symmetrical pattern of light return, as well. It is not a simple, one number, solution in the quest to define the region of what humans believe is in the family of the "most beautiful" set of diamond appearances..