Question about HCA Score and Diamond Depth

MedicalMystery21 · May 1, 2015

Hello, this is my first post here on PS! I have a question regarding HCA scores of super ideal cut diamonds in regards to their depth. After extensive searching, I have narrowed down my quest for the perfect diamond to a few WF ACA stones. I thought I had my mind made up on a stone until I entered the stones into the HCA tool, just for fun/educational purposes. All of the stones I was considering were under 2 and they all received "Excellent" marks in all of the categories except "spread." However, the stone I was leaning towards gave "Very Good" results for brilliance and scintillation as opposed to excellent. It also gave the highest score of 1.8... Not only that, but the X in the diagram was outside the White Box that is supposed to be the AGS ideal zone??? Should this be a red flag? I did some research and found out that the HCA punishes deeper cut stones. Do you think these cut proportions are enough to alter the sparkle of the stone on a visual level? I also notice a bit of green shining through on the ASET image under the table. More cause for concern? (I would post all of these images, but I am unsure how to get pictures onto the threads

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I am very new to this, so pardon my ignorance. Any other advice on the stone is welcome!

http://www.whiteflash.com/loose-diamonds/round-cut-loose-diamond-3186645.htm?

John P · May 2, 2015

Welcome to Pricescope.

The HCA is unnecessary in your case, because you have far more meaningful information. From a prior reply:

1.0 versus 1.8 is irrelevant. It's like putting two cars on a "HCA radar gun." One is going 55. The other 45. Neither is speeding, so the HCA qualifies them as "safe" drivers, but there is not enough info to know which one is ultimately the SAFER driver. You need to get to know the drivers and put them through many more paces to make a more detailed determination. Even then, there are details that remain unaccounted-for.

The HCA does not take the 40 minor facets into consideration (of 57 total on the diamond). It does not account for cut-consistency. It does not account for 3D optical precision. It does not account for indexing. The HCA is blind to all of those things. You have a wealth of data in all of those areas, which trumps HCA output.

What the HCA does it to imagine a "chalk outline" of averaged Table, Crown and Pavilion data, and predict whether the presumed angles may be "safe" or not. That's all. Its intended use is very general: Among global output it rejects some diamonds and IDs others it predicts to be worth further consideration. It should not be used for selection.

Furthermore (not applicable to your case but to others): When using GIA reports the HCA output becomes a bit more uncertain: Because of rounding, GIA 57T 34.5C 40.8P could actually be 57T 34.3 40.7 or 57T 34.7C 40.9P. That toggles between HCA 1.3 to 1.8. So a single diamond can vary on the HCA, simply based on how the lab reports the information.

In Context:

Imagine that you're trying to get to know someone's looks and personality...

An HCA score is like having a chalk outline of the person.
Grading report numbers are like having the person's height, weight and clothing measurements.
An ASET or Ideal-Scope (for RB) image is like having a still photo of the person.
An AGS Platinum "0" in performance is like a panel of judges confirming that the person's personality and looks are solid.
A 3D scan in sophisticated cut-calculation software is like having a video interview with the person.

Eventually, it's a lot of great information. All told it's enough for an experienced cut-specialist to make very detailed performance predictions. But in the end, a live date (dinner & a movie?) will be how you finally judge total personality and looks as you, individually, perceive them.

Prior discussion here:
https://www.pricescope.com/community/threads/hca-score-of-9-vs-1-9-which-is-a-better-score.199300/