Cut Grading Discrepancy between GIA and HCA

[FIREnICE2009]

I''m looking to purchase 1.53ct, round, F,VVS2, X cut, X polish, X symmetry (see below for specs). According to the latest rapapport, the price/ct is 16,300, which will put a 1.53 just below $25k. I''m able to pick this diamond up for $20k which is 20% under rap. This seems like a great deal considering for X cut diamonds, jewelers will charge at least 5-10% premium over rap. What I''m worried about is that this diamond didn''t great as well on the Holloway Cut Advisor (4.3 with ''good'' in 3 of 4 catagories and ''very good'' for spread). I was just wondering if anybody could give me their opinions on the cut of this diamond.

Here''s the GIA cert that was just recertified with laser inscription (Jan 28, 2009):

Round, 1.53 ct
7.43-7.47 X 4.54mm
Color: F
Clarity: VVS2 (cloud & pinpoint)
Cut: Ex
Polish: Ex
Symmetry: Ex
Fluorescence: None
Girdle: Medium. faceted
Table: 59%
Depth: 60.9%
Crown angle: 33.5
Crown height: 13.5%
Pavilion angle: 41.4
Pavilion depth: 44%
Star length: 50%
Culet: none

thanks!

 

[stone-cold11]

GIA Ex grade allows for some diamond geometry that falls in what we call the steep/deep region. This region''s pavilion angle is too big for the corresponding crown angle resulting in light leakage from the pavilion of the diamond resulting in a less brilliant diamond. The stone you picked is one of these unfortunately.

 

[John P]

Date: 1/29/2009 4:58:06 PM
Author:FIREnICE2009

I''m looking to purchase 1.53ct, round, F,VVS2, X cut, X polish, X symmetry (see below for specs). According to the latest rapapport, the price/ct is 16,300, which will put a 1.53 just below $25k. I''m able to pick this diamond up for $20k which is 20% under rap. This seems like a great deal considering for X cut diamonds, jewelers will charge at least 5-10% premium over rap.

I believe a better basis for comparison than Rap is the Pricescope search engine. It uses real examples in real time and actually includes a degree of cut assessment where rap doesn''t.

What I''m worried about is that this diamond didn''t great as well on the Holloway Cut Advisor (4.3 with ''good'' in 3 of 4 catagories and ''very good'' for spread). I was just wondering if anybody could give me their opinions on the cut of this diamond.

The pavilion angle is on the steep side, which could indicate some areas of leakage. Considering the 59% table I''d want to know what the lower half lengths are (not included in your list).

FYI, the GIA EX range is centered a bit steeper than other popular systems. There is a lot of agreed overap from the more accepted metrics but they do have differences. Pavilion angle is what many consider the most critical element. It''s usually good for showing where the ‘center’ of different systems... For 53-58% tables, you will find that pavilion angles 40.6-41.0 have the greatest approval cross-system. The AGS cut guidelines suggest most 0 candidates right in that range. The HCA and AGA prefer the shallow side and a bit lower. The GIA system prefers the steep side and higher.

We could give you more input with an AGS ASET or Ideal-Scope image. These show details of the whole diamond and all facets, whereas the GIA report only gives rounded averages for crown angle, pavilion angle and stars (one number to represent 8 measurements) and lower halves (one number represents 16 measurements). Those averages are like having a chalk outline of a blind date indtead of an actual photo (or 3D scan) beforehand.

 

[Regular Guy]

Fire, personally, IF I wanted the F & VVS2, I''d look fora deal and pay the 2K, maybe getting something like this.

But, you''ll see my prejudice here, and you don''t need the VVS2. But that''s another story.

By the way, I''ve glanced at John''s comments, above. He IS a legend here you know, mentions AGS as a reference, and in seeking out a diamond with that pedigree, I found the one above.

 

[John P]

Date: 1/29/2009 5:15:46 PM
Author: Stone-cold11
GIA Ex grade allows for some diamond geometry that falls in what we call the steep/deep region. This region''s pavilion angle is too big for the corresponding crown angle resulting in light leakage from the pavilion of the diamond resulting in a less brilliant diamond. The stone you picked is one of these unfortunately.

It''s a borderline combo SC. 41.4/33.5, if cut with good precision, can still be an AGS0-1 candidate with a 59% table. However the other details of cut - especially the variance in PA - would need to align perfectly. Even so, it''s not likely to have the balance of fire in performance qualities that one would see with steeper CA, smaller table. But that''s a matter of taste.

 

[John P]

Date: 1/29/2009 5:21:37 PM
Author: Regular Guy
Fire, personally, IF I wanted the F & VVS2, I''d look fora deal and pay the 2K, maybe getting something like this.

But, you''ll see my prejudice here, and you don''t need the VVS2. But that''s another story.

By the way, I''ve glanced at John''s comments, above. He IS a legend here you know, mentions AGS as a reference, and in seeking out a diamond with that pedigree, I found the one above.

Legend?
http://www.youtube.com/watch?v=G2y8Sx4B2Sk

(thx Ira)

 

[stone-cold11]

Date: 1/29/2009 5:21:59 PM
Author: John Pollard

Date: 1/29/2009 5:15:46 PM
Author: Stone-cold11
GIA Ex grade allows for some diamond geometry that falls in what we call the steep/deep region. This region''s pavilion angle is too big for the corresponding crown angle resulting in light leakage from the pavilion of the diamond resulting in a less brilliant diamond. The stone you picked is one of these unfortunately.

It''s a borderline combo SC. 41.4/33.5, if cut with good precision, can still be an AGS0-1 candidate with a 59% table. However the other details of cut - especially the variance in PA - would need to align perfectly. Even so, it''s not likely to have the balance of fire in performance qualities that one would see with steeper CA, smaller table. But that''s a matter of taste.

Ok, I should but in a qualifier, ''some light leakage''. Not extreme. Could still be good depending of the IS as GIA rounds pavilion angles to nearest 0.2 degrees.

 

[Regular Guy]

Date: 1/29/2009 5:25:13 PM
Author: John Pollard

Date: 1/29/2009 5:21:37 PM
Author: Regular Guy
Fire, personally, IF I wanted the F & VVS2, I''d look fora deal and pay the 2K, maybe getting something like this.

But, you''ll see my prejudice here, and you don''t need the VVS2. But that''s another story.

By the way, I''ve glanced at John''s comments, above. He IS a legend here you know, mentions AGS as a reference, and in seeking out a diamond with that pedigree, I found the one above.

Legend?
http://www.youtube.com/watch?v=G2y8Sx4B2Sk

(thx Ira)

Hmmm at my office, where I am now, I have no volume, but I think we''ve been here before....

 

[Lorelei]

Date: 1/29/2009 5:25:13 PM
Author: John Pollard

Date: 1/29/2009 5:21:37 PM
Author: Regular Guy
Fire, personally, IF I wanted the F & VVS2, I''d look fora deal and pay the 2K, maybe getting something like this.

But, you''ll see my prejudice here, and you don''t need the VVS2. But that''s another story.

By the way, I''ve glanced at John''s comments, above. He IS a legend here you know, mentions AGS as a reference, and in seeking out a diamond with that pedigree, I found the one above.

Legend?
http://www.youtube.com/watch?v=G2y8Sx4B2Sk

(thx Ira)

And a rock star.

And a gentle knight.

 

[FIREnICE2009]

thanks for all the quick responses!

John, the Lower-Half Length is 80%. BTW, why is it that AGA prefer a shallow pavilion angle, where as the GIA system leans on the steeper side?

I guess what i want to know is that given it''s limitations (ie, slightly steep pav angle), do you think this is still a good buy at 20K?


-FIREnICE2009

 

[Regular Guy]

No.

 

[John P]

Date: 1/29/2009 7:23:06 PM
Author: FIREnICE2009
thanks for all the quick responses!

John, the Lower-Half Length is 80%. BTW, why is it that AGA prefer a shallow pavilion angle, where as the GIA system leans on the steeper side?

80% is good for that combo. AGA, AGS and HCA are all centered a bit shallower than GIA. The technical reason is the obstruction metric GIA utilized; closer viewing distance favoring deeper stones. The practical reasons are debated...search GIA steep deep and you'll find plenty of speculation.

I guess what i want to know is that given it's limitations (ie, slightly steep pav angle), do you think this is still a good buy at 20K?

Impossible to know without more information. The diamond could be consistently cut, with beautiful precision and optics, or it could have big swings in the main angles causing leakage zones. A quick search on the landing page puts GIA/AGS 1.50-1.60 F VVS2 offerings between $18-30K - so your basic numbers and odds are good - but whether I think it is a good buy would depend entirely on cut details the report doesn't show. I am sorry I can't be more specific.

 

[Dancing Fire]

Date: 1/29/2009 7:23:06 PM
Author: FIREnICE2009
thanks for all the quick responses!

John, the Lower-Half Length is 80%. BTW, why is it that AGA prefer a shallow pavilion angle, where as the GIA system leans on the steeper side?

I guess what i want to know is that given it''s limitations (ie, slightly steep pav angle), do you think this is still a good buy at 20K?


-FIREnICE2009

IMO...that''s why you were able to buy this stone at 20% off of RAP.