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HCA vs. GIA excellent

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Rough_Rock
Joined
Feb 24, 2007
Messages
62
Hello,

I have just bought a GIA certified excellent cut diamond but and it scores 2.2 on the HCA which isn''t "excellent" but "very good" by HCA standards. Does this mean my stone isn''t as excellent a cut as I think it might be although graded on the GIA cert as excellent? I haven''t seen the stone yet but is something that ranks 2.2 on the HCA mean it doesn''t have great visual performance?

These are the parameters of the stone:

GIA certified nov 2006
size 2.2 ct RB
8.40 x 8.43 x 5.15 mm
clarity VS2
colour D
cut excellent
depth 61.2%
table 56%
crown angle 35%
pavillion angle 41%
girdle thin to medium
culet none
fluorescence medium blue
polish excellent
symmetry excellent
comments: additional twining wisps and surface inclusion not shown
Price about USD$28000

Thanks for your comments.
Sharon
 

Ellen

Super_Ideal_Rock
Joined
Jan 13, 2006
Messages
24,427
Hi sharr,

The reason you got a score over 2 (or very good) is because of the combination of crown and pavillion angles. The HCA is in the process of being revised, your stone in the future would get an excellent.

It sounds like it could be a lovely stone. Are you buying online?
 

Unearthed

Shiny_Rock
Joined
Feb 14, 2007
Messages
103
The HCA isn''t a say all end all, it''s one of the many tools used to look at a diamond. 28k for that diamond would seem to be an excellent deal, the spread seems really big for that carat weight.
 

JohnQuixote

Ideal_Rock
Joined
Sep 9, 2004
Messages
5,212
Date: 3/4/2007 5:41:55 AM
Author:sharr
Hello,

I have just bought a GIA certified excellent cut diamond but and it scores 2.2 on the HCA which isn't 'excellent' but 'very good' by HCA standards. Does this mean my stone isn't as excellent a cut as I think it might be although graded on the GIA cert as excellent? I haven't seen the stone yet but is something that ranks 2.2 on the HCA mean it doesn't have great visual performance?

These are the parameters of the stone:

GIA certified nov 2006
size 2.2 ct RB
8.40 x 8.43 x 5.15 mm
clarity VS2
colour D
cut excellent
depth 61.2%
table 56%
crown angle 35%
pavillion angle 41%
girdle thin to medium
culet none
fluorescence medium blue
polish excellent
symmetry excellent
comments: additional twining wisps and surface inclusion not shown
Price about USD$28000

Thanks for your comments.
Sharon
Sharr, it sounds like a beautiful stone.

With regard to PA and CA:GIA rounds some of the numbers on its reports so it’s possible the PA/CA combo is actually 40.9/34.8 (a 1.7 on the HCA) or…it could be a bit on the higher side of 41/35, which would be a higher HCA number. Just FYI. Either way, the indications are good; the diamond has excellent spread for its weight and is worth a further look in my opinion, especially since Ds in 2+ ct sizes are not as abundant as others.A Sarin/Helium report or ideal-scope image from the seller would help secure a sight-unseen cut endorsement here on PS, but your own eyes will be the real test.

As the above posters said, the HCA is a screening tool - to eliminate candidates far out of pocket – and Mr. Holloway is in the process of updating it.
 

Cehrabehra

Super_Ideal_Rock
Joined
Jun 29, 2006
Messages
11,071
Date: 3/4/2007 12:30:15 PM
Author: JohnQuixote

As the above posters said, the HCA is a screening tool - to eliminate candidates far out of pocket – and Mr. Holloway is in the process of updating it.
sorry for the threadjack.... but john and ellen... I see you both have mentioned an HCA update underway... is there a thread where garry discussed this? I''ve been sick and not able/willing to follow some of these intense techy threads, but if there is one about this I''d like to go back and read it! TIA!!
 

Regular Guy

Ideal_Rock
Joined
Jul 6, 2004
Messages
5,954
Date: 3/4/2007 4:50:29 PM
Author: Cehrabehra

Date: 3/4/2007 12:30:15 PM
Author: JohnQuixote

As the above posters said, the HCA is a screening tool - to eliminate candidates far out of pocket – and Mr. Holloway is in the process of updating it.
sorry for the threadjack.... but john and ellen... I see you both have mentioned an HCA update underway... is there a thread where garry discussed this? I''ve been sick and not able/willing to follow some of these intense techy threads, but if there is one about this I''d like to go back and read it! TIA!!
Cehrabehra,

Most recently, in his last 2 posts on page 2 of the article on top, re: Letter to the Editor...Garry talks a bit about it. Elsewhere, he''s mentioned that the stereo vs mono issue will likely raise the threshold to 2.5 vs 2, or beyond. The notes on this page 2, too, add what seems perspective on a soft timetable.
 

[email protected]

Rough_Rock
Joined
Feb 24, 2007
Messages
62
Thank you everyone! Much reassured.

I bought the stone a week ago and they''re mounting it as we speak. It will be arriving in a about 2 weeks time. Yes I did buy the stone online. I have pics of the stone but no idealscope pics. Will post the completed pictures when I get the ring :)
 

Ellen

Super_Ideal_Rock
Joined
Jan 13, 2006
Messages
24,427
Congrats, and can''t wait to see your pics!
 

Cehrabehra

Super_Ideal_Rock
Joined
Jun 29, 2006
Messages
11,071
Date: 3/4/2007 5:17:59 PM
Author: Regular Guy

Date: 3/4/2007 4:50:29 PM
Author: Cehrabehra


Date: 3/4/2007 12:30:15 PM
Author: JohnQuixote

As the above posters said, the HCA is a screening tool - to eliminate candidates far out of pocket – and Mr. Holloway is in the process of updating it.
sorry for the threadjack.... but john and ellen... I see you both have mentioned an HCA update underway... is there a thread where garry discussed this? I''ve been sick and not able/willing to follow some of these intense techy threads, but if there is one about this I''d like to go back and read it! TIA!!
Cehrabehra,

Most recently, in his last 2 posts on page 2 of the article on top, re: Letter to the Editor...Garry talks a bit about it. Elsewhere, he''s mentioned that the stereo vs mono issue will likely raise the threshold to 2.5 vs 2, or beyond. The notes on this page 2, too, add what seems perspective on a soft timetable.
Very good Ira! Thanks! I''m glad stereo is considered, it''s better than 2D, but I was thinking before bed the other day, won''t it be something when the diamcalc looks more like CG? hehehe :D Hopefully I''ll be feeling better enough to dive into that thread soon lol
 
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