Opinions and drawbacks of these proportions....?

[FB.]

I recently put up a couple of threads regarding stones with un usual characteristics (big crowns, small pavilions) that might have potential.

I decided to turn that on it''s head and think about stones at the other extreme (small crowns, big pavilions) that might have potential.

Here''s a set of proportions that don''t entirely fit Tolkowsky''s ideal, but score very well with GIA, AGS (potential) and HCA - and also with AGA.
I would be interested to hear of the drawbacks associated with similar sets of proportions:

GIA cert
Round brilliant
Cut grade: EX
Polish: VG
Symmetry: EX
Table: 60
Crown angle: 33.0''
Crown height: 13.0%
Star: 50%
Girdle: medium
Pavilion angle: 41.1''
Pavilion depth: 43.5%
Lower half: 80%
Total depth: 59.9%
Culet: none

Thanks,

 

[HVVS]

More brilliance than fire? and there''s some issue with durability with low crown angles. It''s been posted here but I don''t have time to search for it.

 

[Lorelei]

Date: 11/18/2009 8:43:39 AM
Author: HVVS
More brilliance than fire? and there's some issue with durability with low crown angles. It's been posted here but I don't have time to search for it.

Generally agreed to be 32.5 or less CA coupled with a very thin girdle.

FB, this might be a decent 60 60 type, any images?

 

[FB.]

Date: 11/18/2009 8:46:24 AM
Author: Lorelei

Date: 11/18/2009 8:43:39 AM
Author: HVVS
More brilliance than fire? and there's some issue with durability with low crown angles. It's been posted here but I don't have time to search for it.

Generally agreed to be 32.5 or less CA coupled with a very thin girdle.

FB, this might be a decent 60 60 type, any images?

Yes, I was wondering about it having serious potential for a 60/60, since it fits very well into the "on paper" stats for cut grade with four different systems (GIA/AGS/HCA/AGA).
I don't normally dabble with diamonds that have tables above 58/59% or depths less than 60.5-61%, but I'm "in the market" for something different, yet with good performance.
Unfortunately, as is usually the case in the UK; personal inspection is required - no images available.

 

[Lorelei]

Date: 11/18/2009 8:51:00 AM
Author: FB.

Date: 11/18/2009 8:46:24 AM
Author: Lorelei

Date: 11/18/2009 8:43:39 AM
Author: HVVS
More brilliance than fire? and there''s some issue with durability with low crown angles. It''s been posted here but I don''t have time to search for it.

Generally agreed to be 32.5 or less CA coupled with a very thin girdle.

FB, this might be a decent 60 60 type, any images?

Yes, I was wondering about it having serious potential for a 60/60, since it fits very well into the ''on paper'' stats for cut grade with four different systems (GIA/AGS/HCA/AGA).
I don''t normally dabble with diamonds that have tables above 58/59% or depths less than 60.5-61%, but I''m ''in the market'' for something different, yet with good performance.
Unfortunately, as is usually the case in the UK; personal inspection is required - no images available.

 

[John P]

Date: 11/18/2009 8:37:40 AM
Author:FB.

I would be interested to hear of the drawbacks associated with similar sets of proportions:

Probably none if cut consistency is good; meaning no big swings in angles. It''s likely quite brilliant. More brightness than fire in the balance of visual properties with that crown configuration. I''ve seen many such examples that are dynamite.

 

[FB.]

Thanks for the replies.

I was under the general impression that shallower stones and flatter crowns would result in increased brightness, reduced fire, reduced scintillation and increased spread.

But the HCA scores as follows:

Light return: VG
Fire: EX
Scintillation: VG
Spread: EX

Much more fire that I would have guessed - and the upper left part of the HCA chart is normally associated with more brilliance and less fire.
Can anyone explain why HCA may be pointing towards more fire?

 

[Lorelei]

Date: 11/18/2009 12:29:18 PM
Author: FB.
Thanks for the replies.

I was under the general impression that shallower stones and flatter crowns would result in increased brightness, reduced fire, reduced scintillation and increased spread.

But the HCA scores as follows:

Light return: VG
Fire: EX
Scintillation: VG
Spread: EX

Much more fire that I would have guessed - and the upper left part of the HCA chart is normally associated with more brilliance and less fire.
Can anyone explain why HCA may be pointing towards more fire?

Generally so, as you know the HCA is only predicting according to the way it is configured, again no way to know without images.

 

[Rockdiamond]

HI all!

fb- I am very interested in a lot of the things you've mentioned. I was going to respond to your "obstruction" thread later as well.

The stone described in this thread is one I'd LOVE to see.

Without question it's harder to find the larger tabled stones nowadays. Not that 60% is large by any means, but it looks a lot more "open" than 57%.

IMO opening up the top of the diamond gives it a lot more.....of something I love ( be it fire, or scintillation, brilliance or whatever we want to call it)

 

[John P]

Date: 11/18/2009 12:29:18 PM
Author: FB.

Can anyone explain why HCA may be pointing towards more fire?

The HCA is strict on deeper pavilions and likely predicts a reduction in overall LR at 41.1. Indeed, moving PA down to 41.0 results in EX EX VG EX. But (interestingly) moving down to 40.9 results in VG EX VG EX again.

Keep in mind that the HCA is a rejection tool which doesn't know minor facet measurements, cut consistency or brillianteering particulars. As such I find the given factors of LR, Fire and Scint to be more fluid in accuracy than the total visual performance score (0-2, 2-4, etc), which is predicted based on concrete, if averaged, data points.

I would not read too much into it. In this case you have more info on the grading report than the HCA uses to make its prediction.