Help me choose between 2 diamonds!

[prking21]

I am currently in the process of selecting a stone for an e-ring and have it narrowed down to 2, but am having trouble deciding which one to go with based on my limited experience and information that is available.



Both stones are 100% eye clean according to the cutters (I have not physically seen either). The gentlemen that I am working with did say that the cutter from stone A is his preferred cutter to work with and has had more of a mixed experience with the cutter from stone B. Both are GIA certified round brilliant cuts and are the same price.



Stone A:

6.96-6.96x4.26 mm

Carat-1.27

Color-J

Clarity-SI2

Cut- Excellent

Polish- Excellent

Symmetry- Excellent

Fluorescence- None

Table- 60%

Depth- 62.1%

Crown- 34%

Pavilion- 41.2%

Cutlet- None

HCA score= 3.8 (Very good)



Stone B:

7.07-7.11x4.22 mm

Carat-1.30

Color-J

Clarity-SI2

Cut- Excellent

Polish- Excellent

Symmetry- Excellent

Fluorescence- None

Table- 61%

Depth- 59.5%

Crown- 33.5%

Pavilion- 40.8%

Cutlet- None

HCA score= 1.8 (Excellent)

I have read not to put too much weight into the HCA score and the the GIA cut grade is a better indicator. Not sure if this matters but on the website Stone A is listed as a "Signature Ideal Cut" where Stone B is listed as an "Ideal Cut." Is it a problem the the table is bigger than the depth on Stone B? This is all the info I can get unfortunately, so any insight would be greatly appreciated.

Thanks!

 

[Gypsy]

GIA Cut is not a better indicator. And it's clear you don't really understand the HCA. Read below;

The entire purpose of faceting a diamond is to reflect light.
How well or how poorly a diamond does this determines how beautiful it is.
How well a diamond performs is determined by the angles and cutting. This is why we say cut is king.
No other factor: not color, not clarity has as much of an impact on the appearance of a diamond as its cut. An ideal H will out white a poorly cut F. And GIA Ex is not enough. And you must stick to GIA and AGS only. EGL is a bad option: [URL='https://www.pricescope.com/community/threads/egl-certification-are-any-of-them-ok.142863/']https://www.pricescope.com/community/threads/egl-certification-are-any-of-them-ok.142863/[/URL]
So how to we ensure that we have the right angles and cutting to get the light performance we want?
https://www.pricescope.com/wiki/diamonds/diamond-cut
Well one method is to start with a GIA Ex, and then apply the HCA to it. YOU DO NOT USE HCA for AGS0 stones.
https://www.pricescope.com/wiki/diamonds/holloway-cut-advisor
The HCA is a rejection tool. Not a selection tool. It uses 4 data points to make a rudimentary call on how the diamond may perform.
If the diamond passes then you know that you are in the right zone in terms of angles for light performance. Under 2 is a pass. Under 2.5-2.1 is a maybe. 2.6 and over is a no. No score 2 and under is better than any other.
Is that enough? Not really.
So what you need is a way to check actual light performance of your actual stone.
That's what an idealscope image does. https://www.pricescope.com/wiki/diamonds/firescope-idealscope
It shows you how and wear your diamond is reflecting light, how well it is going at it, and where you are losing light return. That is why you won't see us recommending Blue Nile, as they do not provide idealscope images for their diamonds. BGD, James Allen, GOG, HPD, ERD and WF do.

The Idealscope is the 'selection tool'. Not the HCA.
So yes, with a GIA stone you need the idealscope images. Or you can buy an idealscope yourself and take it in to the jeweler you are working with to check the stones yourself. Or if you have a good return policy (full refund minimum 7 days) then you can buy the idealscope, buy the stone, and do it at home.


Now if you want to skip all that... stick to AGS0 stones and then all you have to do is pick color and clarity and you know you have a great performing diamond. Because AGS has already done the checking for you. That's why they trade at a premium.

 

[Gypsy]

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. None of that information is present. The HCA is imagining a "chalk outline" of averaged (sometimes rounded) Table, Crown and Pavilion data, and predicting whether the presumed angles are "safe" or not. That's its intended use, and it's useful in that context; to reject some diamonds - and ID others worth further consideration. It should not be used for selection.

When using GIA reports the 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 (from a prior thread)

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

An HCA score is merely 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.

 

[Gypsy]

edit

Read this: [URL='https://www.pricescope.com/community/threads/help-gia-excellent-cut-vs-hca.177583/']https://www.pricescope.com/community/threads/help-gia-excellent-cut-vs-hca.177583/[/URL] and [URL='https://www.pricescope.com/community/threads/gia-excellent-cut-cut-advisor-5-8-what-to-do.87439/']https://www.pricescope.com/community/threads/gia-excellent-cut-cut-advisor-5-8-what-to-do.87439/[/URL]

 

[prking21]

Wow! Thank you Gypsy for taking the time to educate me! I have a much better idea of how to process all of the different information!

 

[Gypsy]

Happy to help!