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Cut grade Excellent - performs poorly with Holloway Cut Advisor tool

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waikay

Rough_Rock
Joined
Jan 30, 2007
Messages
4
Help! I''m thinking about buying this diamond for the engagement ring, but I''m really confused about the Cut Grade vs. the results I got from the Holloway Cut Advisor tool.

Here are the diamond specs from the GIA cert:
1.21 carat Round Brilliant
Color: E
Clarity: VS2
Cut Grade: Excellent
Polish: Very Good
Symmetry: Very Good
Fluorescence: None
Table: 59%
Depth: 61.8%
Crown: 35 degrees
Paviliion: 41.4 degrees
Cutlet: none
Girdle: Medium - slightly thick (faceted)
Price is $8,800

I used the Holloway Cut Advisor tool and didn''t get the results that I expected from an "Excellent" cut diamond. Here are the results:
Light Return - Good
Fire - Fair
Scintillation - Fair
Spread - Very Good
Total Visual Performance - 5.2 - Good - Only if price is your main criterion

I thought that this diamond would perform either excellent or very good and I''m suprised to see that it recieved "Fair" and "Good" results.
Could somebody please explain why this diamond with a Cut Grade of Excellent with Very Good Polish and Symmetry get "Fair" and "Good" results from the Holloway Cut Advisor? Is this a nice diamond to buy?

Is $8,800 a good price for this diamond?

THANKS IN ADVANCE for your feedback
 

tanalasta

Shiny_Rock
Premium
Joined
Dec 28, 2006
Messages
323
I would definitely conider paying the extra few hundred (and if you include the PS and bank wire discount, the round ideal from whiteflash is actually about the same price if not cheaper!!!) for the whiteflash diamond which potentially is a nicer cut.

The GIA excellent steeper and deeper diamonds usually fall short. i.e. the crown / pavillion angle combination is steeper than what most would consider ideal.The GIA excellent grading has received a fair amount of controversy and is a broader category based upon proportion sets derived from so-called 'observation' (in itself, the study the GIA based it's grading on is controversial) than the AGS ideal which have a stricter criteria based on actual light performance on a stone-by-stone basis.

I wouldn't buy the diamond you mentioned. The GIA 'excellent' system isn't perfect unless you looked at the diamond and really loved it.

The HCA is only a tool - not a definitive guide and often penalises steep/deep diamonds (although in this case - perhaps rightfully so)

The 'round ideal' on whiteflash could also be a better stone in that it's not that tightly cut. I also suspect that it may fall slightly short of AGS '0' light performance - hence why it seems to have the old certificate unless I am mistaken.
 

JulieN

Super_Ideal_Rock
Premium
Joined
Jul 25, 2005
Messages
13,324
Date: 1/31/2007 3:36:08 AM
Author: tanalasta
The 'round ideal' on whiteflash could also be a better stone in that it's not that tightly cut. I also suspect that it may fall slightly short of AGS '0' light performance - hence why it seems to have the old certificate unless I am mistaken.
Dated Oct 2006. All Expert Selection stones carry Diamond Quality Reports and not Documents.

ASET is by the book.
 

Rhino

Ideal_Rock
Trade
Joined
Mar 28, 2001
Messages
6,272
Date: 1/31/2007 2:54:43 AM
Author:waikay
Help! I''m thinking about buying this diamond for the engagement ring, but I''m really confused about the Cut Grade vs. the results I got from the Holloway Cut Advisor tool.

Here are the diamond specs from the GIA cert:
1.21 carat Round Brilliant
Color: E
Clarity: VS2
Cut Grade: Excellent
Polish: Very Good
Symmetry: Very Good
Fluorescence: None
Table: 59%
Depth: 61.8%
Crown: 35 degrees
Paviliion: 41.4 degrees
Cutlet: none
Girdle: Medium - slightly thick (faceted)
Price is $8,800

I used the Holloway Cut Advisor tool and didn''t get the results that I expected from an ''Excellent'' cut diamond. Here are the results:
Light Return - Good
Fire - Fair
Scintillation - Fair
Spread - Very Good
Total Visual Performance - 5.2 - Good - Only if price is your main criterion

I thought that this diamond would perform either excellent or very good and I''m suprised to see that it recieved ''Fair'' and ''Good'' results.
Could somebody please explain why this diamond with a Cut Grade of Excellent with Very Good Polish and Symmetry get ''Fair'' and ''Good'' results from the Holloway Cut Advisor? Is this a nice diamond to buy?

Is $8,800 a good price for this diamond?

THANKS IN ADVANCE for your feedback
A 35/41.4 combo will produce leakage that begins to become visible. Its a stone that would more than likely get the AGS 1 for light performance, maybe a 2 as it doesn''t fall in the zenith of GIA/AGS top specs. Before you pull the trigger on it a wise thing to do would be to *see it* alongside another GIA Ex with shallower angles (if the person you''re doing business with only carries GIA stones) with crown angles at or under 35 degrees and pavilion angles no greater than 41 or an AGS Ideal. Then make your comparison and buy what appeals most to your eyes.

Good luck on your hunt.
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
15,305
Date: 1/31/2007 11:31:44 AM
Author: Rhino

A 35/41.4 combo will produce leakage that begins to become visible. Its a stone that would more than likely get the AGS 1 for light performance, maybe a 2 as it doesn''t fall in the zenith of GIA/AGS top specs. Before you pull the trigger on it a wise thing to do would be to *see it* alongside another GIA Ex with shallower angles (if the person you''re doing business with only carries GIA stones) with crown angles at or under 35 degrees and pavilion angles no greater than 41 or an AGS Ideal. Then make your comparison and buy what appeals most to your eyes.

Good luck on your hunt.
Rhino check the top of the Diamcalc image above - those proportions give AGS 5 candidate results.
 

waikay

Rough_Rock
Joined
Jan 30, 2007
Messages
4
Thanks everyone for your feedback! This forum is a wonderful resource.
 

Rhino

Ideal_Rock
Trade
Joined
Mar 28, 2001
Messages
6,272
Date: 1/31/2007 2:28:39 PM
Author: Garry H (Cut Nut)

Date: 1/31/2007 11:31:44 AM
Author: Rhino

A 35/41.4 combo will produce leakage that begins to become visible. Its a stone that would more than likely get the AGS 1 for light performance, maybe a 2 as it doesn''t fall in the zenith of GIA/AGS top specs. Before you pull the trigger on it a wise thing to do would be to *see it* alongside another GIA Ex with shallower angles (if the person you''re doing business with only carries GIA stones) with crown angles at or under 35 degrees and pavilion angles no greater than 41 or an AGS Ideal. Then make your comparison and buy what appeals most to your eyes.

Good luck on your hunt.
Rhino check the top of the Diamcalc image above - those proportions give AGS 5 candidate results.
Just had the chance to check into this further. Turns out we''re both wrong.
It''s neither a 5 or a 1-2. I duped your model and ran it through PGS. Comes out to a 3. I entered Ideal polish/symmetry to just see the light performance metric. Are the predictions in DiamCalc based on the AGS tables?

Regards,

br121evspgs.gif
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
15,305
Date: 2/1/2007 5:46:48 PM
Author: Rhino

Date: 1/31/2007 2:28:39 PM
Author: Garry H (Cut Nut)


Date: 1/31/2007 11:31:44 AM
Author: Rhino

A 35/41.4 combo will produce leakage that begins to become visible. Its a stone that would more than likely get the AGS 1 for light performance, maybe a 2 as it doesn''t fall in the zenith of GIA/AGS top specs. Before you pull the trigger on it a wise thing to do would be to *see it* alongside another GIA Ex with shallower angles (if the person you''re doing business with only carries GIA stones) with crown angles at or under 35 degrees and pavilion angles no greater than 41 or an AGS Ideal. Then make your comparison and buy what appeals most to your eyes.

Good luck on your hunt.
Rhino check the top of the Diamcalc image above - those proportions give AGS 5 candidate results.
Just had the chance to check into this further. Turns out we''re both wrong.
It''s neither a 5 or a 1-2. I duped your model and ran it through PGS. Comes out to a 3. I entered Ideal polish/symmetry to just see the light performance metric. Are the predictions in DiamCalc based on the AGS tables?

Regards,
Yes - DiamCalc has the AGS ''Candidate'' charts programmed in, with a handy button to calculate the least weight loss to raise the AGS grade - like a recut button.

The method you used assumes a totally perfect diamond - and we know that in such cases we can find stones that are poutside their ''Candidate'' zones - but since the symmetry and polish of this stone are GIA VG -it is unlikely that it would score very well if you had a real stone scan Rhino.
 
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