discrepancy between HCA and GIA tables

[BayouKip]

Can someone explain to me the discrepancy between the HCA and GIA tables in regard to a diamond with the following measurements:

Depth:
61.4%
Table:
58%
Crown:
34 degrees
Pavilion
41.4 degrees

The hca gives a value of 4.7, however the GIA tables list it well within the excellent cut regions http://www.gia.edu/diamondcut/pdf/booklet_cut_estimation_tables_lowres.pdf

Thanks for the help!

 

[JulieN]

There is a difference of opinion.

I would look for another diamond.

 

[BayouKip]

Right, I guess what I am asking is both plot crown and pavilion angles as a function of table %, in what way are the two opinions so radically different, im trying to get an idea for what it would look like in real life

 

[JulieN]

There is some concern of visible leakage. Here is a related article: https://www.pricescope.com/journal/do_pavilion_mains_drive_light_return_modern_round_brilliant

 

[Stone-cold11]

This article too.

https://www.pricescope.com/journal/laboratory_cut_grades_what_report_doesn’t_show

 

[Rockdiamond]

It's true- there are many differing opinions.
Speaking in general terms: I look at each diamond holistically.
What I mean is, if I'm looking at a 1.00 D/VS1, I might agree with the type of stone the HCA would prefer.
If it's a 5.65ct M/VS1, it would very likely be , for me at least, a different type of stone I'd prefer.

Is this a stone you are looking at in person?

 

[BayouKip]

Unfortunately not, I'm looking at a lot of different stones online. I'm an amateur. I'm looking for some sort of consensus on with the different models (GIA, AGS, HCA).

 

[slg47]

GIA, AGS, and HCA use different parameters for cut. In general I think you are safest with AGS ideal (usually don't need HCA here) or GIA Ex with HCA < 2. Pictures and idealscope images can also help you evaluate cut.

 

[Rockdiamond]

Unfortunately not, I'm looking at a lot of different stones online. I'm an amateur. I'm looking for some sort of consensus on with the different models (GIA, AGS, HCA).

There's not going to ever be a consensus on which table and depth/ PA/CA LGF combo is best. GIA's range is wider than AGSL- these are the two accepted cut grades by the trade at large.
It's a range. GIA's range is wider- some could argue that makes AGSL a "better" cut grade.
I look at it holistically. Gotta look at the diamond to know
If you could look at some diamonds in real life- hopefully some with GIA, or AGSL reports, you'd have a much better starting point.

 

[JulieN]

I agree that it's important to consider many factors. As for myself, I find GIA cut grading to be unusable as a method of comparing stones.