Any concerns on this RB?

[ragscotty]

I dont have any information aside from the HCA 1.4 and numbers.

1.35 G Si1 ex/ex/vg 7.02-7.08x4.39
table 56
depth 62.3
paviliion 34.5
crown 40.8

Thanks.

 

[YoungPapa]

ragscotty,

I proposed to my wife many years ago with a G-SI1. Needless to say, I''m partial to that combination. The cut looks great, just make sure the SI1 isn''t something you don''t see and she might. It''s unlikely, but double check. If the lab report isn''t from GIA, triple check.

 

[John P]

Date: 2/26/2009 11:06:19 PM
Author:ragscotty
I dont have any information aside from the HCA 1.4 and numbers.

1.35 G Si1 ex/ex/vg 7.02-7.08x4.39
table 56
depth 62.3
paviliion 34.5
crown 40.8

Thanks.

The average angles are good. The depth indicates it's carrying some extra in the girdle as it faces up like a 1.27 with those proportions and GIA med girdle. Since it's EX in cut the girdle max is stk which is fine.

Although those few numbers are good they give no indication of cut consistency or precision. 40.8 could mean that all eight pavilion mains were cut consistency near 40.8, or it could imply a wider swing of angles that average to 40.8 but result in leakage zones. The details of the minor facets influence the character of performance too; 75% lower halves will look quite different than 85%. And of course you should check out the quality of that SI1 grade as far as visibility of inclusions goes.

This means the best we can say with the limited info is "so far so good." An ideal-scope or ASET image would get you more meaningful performance predictions.

 

[YoungPapa]

John,

You know I'm a fan. Well, maybe you don't - I'm a fan.

With that said, assuming this is a GIA graded eye-clean diamond, do you really believe "so far, so good" is the best conclusion? With a 34.5 crown/40.8 pavilion (average or otherwise) I don't think it says "good" on that hypothetical GIA report.

How about we consider the glass half-full and call it "So Far, So Excellent"!

 

[John P]

Thanks Jim - and back at you.

So far so good is all I would say until someone sees the diamond.

We can't know if "40.8 PA," an average of eight measurements, represents a total range of 40.7-40.9 (example) or 40.2-41.4 which could be a mess. Same with CA though not as critical as pavilion. Moreover, the lower halves account for more surface area on the pavilion than the mains and we have no info on their cut consistency.

Here's an example. This GIA EX EX EX (report) has basics of 57/41/35. Those numbers seem good but the IS and ASET generated by a scan of that diamond reveal the swings from a single numerical 'average.' They're wide enough to create leakage zones which wouldn't be present if the diamond was cut with better consistency/precision.

There is just no way to know if such swings exist from a few rounded averages on the report. That is why ideal-scope or ASET are (for me) compulsory. I am a fan of GIA and AGS but no system (to me) is perfect. Give me actual imagery showing what's happening to the light inside that diamond. Even better, let me play with it in person!

Many diamonds I see with those basic numbers are beautiful (you too I suspect). Even so, examples like the above are out there so my rule is "trust but verify." I will also admit to being very analytic. Still, a diamond considered in any thread could be the only one that person ever buys, so I go through all the motions and precautions as if I were buying it for myself. Scratch that, I meant for my wife of course!

 

[diagem]

Date: 2/27/2009 12:33:07 AM
Author: John Pollard
Thanks Jim - and back at you.

So far so good is all I would say until someone sees the diamond.

We can''t know if ''40.8 PA,'' an average of eight measurements, represents a total range of 40.7-40.9 (example) or 40.2-41.4 which could be a mess. Same with CA though not as critical as pavilion. Moreover, the lower halves account for more surface area on the pavilion than the mains and we have no info on their cut consistency.

Here''s an example. This GIA EX EX EX (report) has basics of 57/41/35. Those numbers seem good but the IS and ASET generated by a scan of that diamond reveal the swings from a single numerical ''average.'' They''re wide enough to create leakage zones which wouldn''t be present if the diamond was cut with better consistency/precision.

There is just no way to know if such swings exist from a few rounded averages on the report. That is why ideal-scope or ASET are (for me) compulsory. I am a fan of GIA and AGS but no system (to me) is perfect. Give me actual imagery showing what''s happening to the light inside that diamond. Even better, let me play with it in person!

Many diamonds I see with those basic numbers are beautiful (you too I suspect). Even so, examples like the above are out there so my rule is ''trust but verify.'' I will also admit to being very analytic. Still, a diamond considered in any thread could be the only one that person ever buys, so I go through all the motions and precautions as if I were buying it for myself. Scratch that, I meant for my wife of course!

Interesting point John..., whats the allowed average angle range by GIA/AGS to stay withing the 0/EX-EX-EX area?

 

[John P]

Date: 2/27/2009 1:12:14 AM
Author: DiaGem

Interesting point John..., whats the allowed average angle range by GIA/AGS to stay withing the 0/EX-EX-EX area?

At GIA the 2D averages are used to determine the proportions grade - I'm not aware of them calculating variance but they do use scan data to make brillianteering judgments. Crown angle and pavilion angle variation are listed under visual symmetry grading (like a wavy girdle or missing facets) but I'd think they'd need to be pretty severe to be visible to a grader. As I recall the lower halves are the culprits in the example above anyway, so there was no catching it.

At AGS variation is accounted-for since the whole diamond is scanned and ray-traced in 3D. Leakage will cause it to take a hit in brightness.

 

[diagem]

Date: 2/27/2009 1:34:57 AM
Author: John Pollard

Date: 2/27/2009 1:12:14 AM
Author: DiaGem

Interesting point John..., whats the allowed average angle range by GIA/AGS to stay withing the 0/EX-EX-EX area?

At GIA the 2D averages are used to determine the proportions grade - I''m not aware of them calculating variance but they do use scan data to make brillianteering judgments. Crown angle and pavilion angle variation are listed under visual symmetry grading (like a wavy girdle or missing facets) but I''d think they''d need to be pretty severe to be visible to a grader. As I recall the lower halves are the culprits in the example above anyway, so there was no catching it.

At AGS variation is accounted-for since the whole diamond is scanned and ray-traced in 3D. Leakage will cause it to take a hit in brightness.

How about a mess in the usual uniform patterns?

 

[John P]

Date: 2/27/2009 1:44:26 AM
Author: DiaGem

Date: 2/27/2009 1:34:57 AM
Author: John Pollard

Date: 2/27/2009 1:12:14 AM
Author: DiaGem

Interesting point John..., whats the allowed average angle range by GIA/AGS to stay withing the 0/EX-EX-EX area?

At GIA the 2D averages are used to determine the proportions grade - I'm not aware of them calculating variance but they do use scan data to make brillianteering judgments. Crown angle and pavilion angle variation are listed under visual symmetry grading (like a wavy girdle or missing facets) but I'd think they'd need to be pretty severe to be visible to a grader. As I recall the lower halves are the culprits in the example above anyway, so there was no catching it.

At AGS variation is accounted-for since the whole diamond is scanned and ray-traced in 3D. Leakage will cause it to take a hit in brightness.

How about a mess in the usual uniform patterns?

A 'mess' is usually due to variance which contributes to leakage or sometimes obstruction. The role of the lower halves shouldn't be underestimated here.

Clearly defined patterns improve contrast in brilliants and princess cuts. Uniformity can keep it in balance. I think the biggest impact of uniform patterns will be uncovered as scintillation is studied more - the preliminary work seems to show that. Right now the two labs discussed have done most of their work judging brightness. While their systems have strong points it's really only one 'view' being evaluated (granted, AGS incorporats tilt to compass points in their LP grade).

On a different topic, same question, I agree - in principal since I can rarely find SE with AGS reports - with something you or Karl said some days ago about a need for putting weight on patterns in cut assessment of step cuts.

To the OP, sorry for the threadjack.

This post has naught to do with your question.

 

[Lorelei]

Great conversation and very interesting, thanks chaps!!

rags, if you could get images of the diamond then that would be helpful as you have learned, the diamond looks promising.

 

[diagem]

Date: 2/27/2009 2:09:45 AM
Author: John Pollard

Date: 2/27/2009 1:44:26 AM
Author: DiaGem

Date: 2/27/2009 1:34:57 AM
Author: John Pollard

Date: 2/27/2009 1:12:14 AM
Author: DiaGem

Interesting point John..., whats the allowed average angle range by GIA/AGS to stay withing the 0/EX-EX-EX area?

At GIA the 2D averages are used to determine the proportions grade - I''m not aware of them calculating variance but they do use scan data to make brillianteering judgments. Crown angle and pavilion angle variation are listed under visual symmetry grading (like a wavy girdle or missing facets) but I''d think they''d need to be pretty severe to be visible to a grader. As I recall the lower halves are the culprits in the example above anyway, so there was no catching it.

At AGS variation is accounted-for since the whole diamond is scanned and ray-traced in 3D. Leakage will cause it to take a hit in brightness.

How about a mess in the usual uniform patterns?

A ''mess'' is usually due to variance which contributes to leakage or sometimes obstruction. The role of the lower halves shouldn''t be underestimated here.

Clearly defined patterns improve contrast in brilliants and princess cuts. Uniformity can keep it in balance. I think the biggest impact of uniform patterns will be uncovered as scintillation is studied more - the preliminary work seems to show that. Right now the two labs discussed have done most of their work judging brightness. While their systems have strong points it''s really only one ''view'' being evaluated (granted, AGS incorporats tilt to compass points in their LP grade).

On a different topic, same question, I agree - in principal since I can rarely find SE with AGS reports - with something you or Karl said some days ago about a need for putting weight on patterns in cut assessment of step cuts.

To the OP, sorry for the threadjack.

This post has naught to do with your question.

Of-course not...

They can help (scattered contrast appearance) or distract/break uniformity..., the result realy depends on personal taste..., you agree?

 

[strmrdr]

Date: 2/27/2009 6:53:15 AM
Author: DiaGem
They can help (scattered contrast appearance) or distract/break uniformity..., the result realy depends on personal taste..., you agree?

When it comes to scintillation No I think its a performance issue, but I haven't come up with the proof that will stand up to peer review but I am working on it.

But from a leakage stand point when it comes to the lower girdles John is 100% correct.
You can read about it in a few days :}