Fiery Ideal Cut

[FB.]

I came across this stone in recent days and it got me thinking:


Table: 55%
Star: 50%
Crown angle: 38.5'
Crown height: 18.0%
Girdle: thin-medium (faceted)
Pavilion angle: 39.8'
Pavilion depth: 41.5%
Lower half: 75%
Total depth: 62.9%
GIA cut grade: VG
Polish: EX
Symmetry: EX

Does a Fiery ideal cut get much better than that?

Would it benefit from slightly larger star %?
Or slightly larger lower half %?
Is the pavilion too shallow (although it appears to be complementary to the crown angle)?
Are the proportions so extreme that undesirable effects might occur?

(edit: added GIA cut grade, polish and symmetry)

Thanks,

 

[Lorelei]

Date: 11/13/2009 11:09:50 AM
Author:FB.
I came across this stone in recent days and it got me thinking:


Table: 55%
Star: 50%
Crown angle: 38.5'
Crown height: 18.0%
Girdle: thin-medium (faceted)
Pavilion angle: 39.8'
Pavilion depth: 41.5%
Lower half: 75%
Total depth: 62.9%

Does a Fiery ideal cut get much better than that?

Would it benefit from slightly larger star %?
Or slightly larger lower half %?
Is the pavilion too shallow (although it appears to be complementary to the crown angle)?
Are the proportions so extreme that undesirable effects might occur?

Thanks,

It would need checking for obstruction issues FB due to the pavilion angle, if it is ok in that respect it would be very interesting to see this diamond. It is possible it could benefit from longer lower halves.

 

[stone-cold11]

ditto.

 

[FB.]

and if it was mounted in a pendant.......?

 

[stone-cold11]

Should not be a problem then.

 

[Upgradable]

I''m a sucker for FIBs!! I would love to see this stone in a pendant, moving a little catching the light!

 

[Lorelei]

Date: 11/13/2009 11:28:22 AM
Author: Stone-cold11
Should not be a problem then.

And ditto

 

[FB.]

Nobody''s worried about possible fish-eye effect from such a shallow pavilion?

 

[Lorelei]

Date: 11/15/2009 8:37:59 AM
Author: FB.
Nobody''s worried about possible fish-eye effect from such a shallow pavilion?

I don''t think it would be an issue for a pendant stone, but of course as you know all of this is speculation without images.

 

[Karl_K]

not a fisheye, but has some serious obstruction going on.

Even in a pendant the mains would be very dark.

This is from 25 inches.

 

[FB.]

Thanks, Karl.

If you had been the cutter, how might you have tried to improve the performance?

 

[Karl_K]

Date: 11/15/2009 2:06:58 PM
Author: FB.
Thanks, Karl.


If you had been the cutter, how might you have tried to improve the performance?

one would assume there was something wrong with the rough that forced it to be cut to those proportions so likely the only thing that could have been done was make it smaller and put a reasonable pavilion angle on it.

 

[FB.]

Thanks again, Karl.

What would you consider to be a good set of proportions for pushing a fiery ideal stone to the absolute limit?

 

[Karl_K]

Date: 11/15/2009 4:13:14 PM
Author: FB.
Thanks again, Karl.

What would you consider to be a good set of proportions for pushing a fiery ideal stone to the absolute limit?

50T/80lgf/37c/40.5P/45stars

 

[FB.]

Thanks. That''s interesting and helpful to know.

 

[FB.]

I saw a second stone that I wondered about.

It seems to fit about as closely as I can ever recall seeing in other stones:

Table: 53%
Star: 50%
Crown angle: 36.5''
Crown height: 17.5%
Girdle: thin-slightly thick (faceted) 4.5%
Pavilion angle: 40.2''
Pavilion depth: 42.0%
Lower half: 80%
Total depth: 63.8%
GIA cut grade: VG
Polish: VG
Symmetry: VG

 

[Karl_K]

40.2'' is on the shallow side will have some issues in a ring
huge girdle

 

[FB.]

Karl,

You mention about obstruction of the stone out to 2ft and beyond, but how would the first stone (38.5/39. be likely to perform, when viewed at a variety of angles?
If I test the numbers in HCA, the stone scores very well and sits at the end of the FIC range - and also doesn't get reported as possible fisheye.

Do you think that the 38.5/39.8 is likely to be a fiery stone, even if it suffers from some obstruction issues?

If I enter the numbers into AGA, the stone gets dumped into the average cut grades, based on a crown that's too big and a pavilion that's too small. But the two seem to match each other very well - especailly as the stone doesn't end up being fisheye.

If I check to see which way the rounding may have occurred by using the (less accurate) percenatge crown and pavilion % numbers, it looks more like the stone is 38.6/39.7.

I'm quite encouraged that the cutter gave such an unusual stone Ex/Ex polish and symmetry. I would be surprised to see a cutter bother with such high polish/symm unless he thought that the stone was a good one.

Thanks for any more input you can give.
Since you have the technology, I'd love to hear the full light-performance profile of this stone as best you can estimate.