Opinion on a stone

[BCR]

I just purchased an RB e ring stone and am waiting for it to be set in the band I chose. Of course I didn''t discover this site until the deal was done. Lots of great information and opinions here - it is a really great resource. Anyway, I did a TON of research before buying and was wondering if the collective here can evaluate my purchase. I think I did well, but it would (of course) been much easier if I had known about this forum first!

GIA cert
size 1.71
H VS2
H&A lazer inscription (not that it means anything - but under the idealscope, the hearts and arrows look VERY crisp, symmetrical, etc...)
depth % 61.8%
table % 57%
crown angle 35%
pavilion angle 43.5%
girdle thickness thin-medium, faceted
polish and symmetry grades ex, ex
diameter measurements 7.67 x 7.71
fluorescence faint

The inclusions are a couple pinpoints and very small feathers that are not directly under the table, so they are VERY difficult to see under the loupe (the inclusions of other stones I looked at were much more obvious). Definitely eyeclean beyond a doubt. I looked at a LOT of stones and the H color designation is maybe a misnomer. It compares much more favorably to the G''s I looked at than the rest of the H''s - it is definitely at the higher end of the H range.

Any comments on the angles? They were within the ranges specified on just about every chart online for an ideal cut. Wish I had the benefit of advice here before purchasing, but would rather at least know now how I did...

 

[Lorelei]

Can you check the pav angle please, I think that is the depth you have posted?

Welcome to PS!

 

[BCR]

sorry - yes, you''re right - typed too fast this morning!

here is the correct info - can''t seem to edit my original post...

GIA cert
size 1.71
H VS2
H&A lazer inscription (not that it means anything - but under the idealscope, the hearts and arrows look VERY crisp, symmetrical, etc...)
depth % 61.8%
table % 57%
crown angle 35%
crown height 15%
pavilion angle 41%
pavillion depth 43.5%
girdle thickness thin-medium, faceted
polish and symmetry grades ex, ex
diameter measurements 7.67 x 7.71
fluorescence faint

 

[stone-cold11]

61.8% depth, 57% table, 35 crown angle, 41 pavilion angle HCA 2.4.

Not excellent, but very good cut.

 

[BCR]

I am a little confused because of the following I found on GOG (not who I bought the stone from) and other places about HCA scores:

Diamonds with 41° pavilion angles (and even slightly over) are among the most beautifully cut diamonds in the world (when coupled with appropriate crown angles). Above we were examining how HCA scores got worse as leakage became more apparent when observed through red reflectors. According to both GIA and AGS laboratories (2 of the most renown and conservative labs in the world) the diamond in the above table with 35 degree crown angles and 41 degree pavilion angles (which gets a so-so HCA score of 2.2) consider this as a top grade and displays what is perhaps some of the best optics to be seen in round brilliant cut diamonds. In the above example the ever so faint amount of leakage in the center diamond and the diamond on the far right is impossible, I repeat, impossible to discern with human vision in any lighting environment you bring the diamond into. It is only something that can barely be seen under a red reflector and even at that it is still very difficult. Take this real diamond below as an example. It serves to demonstrate a few limitations of the HCA.

 

[Lorelei]

Date: 10/5/2008 9:52:09 AM
Author: BCR
I am a little confused because of the following I found on GOG (not who I bought the stone from) and other places about HCA scores:

Diamonds with 41° pavilion angles (and even slightly over) are among the most beautifully cut diamonds in the world (when coupled with appropriate crown angles). Above we were examining how HCA scores got worse as leakage became more apparent when observed through red reflectors. According to both GIA and AGS laboratories (2 of the most renown and conservative labs in the world) the diamond in the above table with 35 degree crown angles and 41 degree pavilion angles (which gets a so-so HCA score of 2.2) consider this as a top grade and displays what is perhaps some of the best optics to be seen in round brilliant cut diamonds. In the above example the ever so faint amount of leakage in the center diamond and the diamond on the far right is impossible, I repeat, impossible to discern with human vision in any lighting environment you bring the diamond into. It is only something that can barely be seen under a red reflector and even at that it is still very difficult. Take this real diamond below as an example. It serves to demonstrate a few limitations of the HCA.

BCR, with the 35/41 combo, it is entering what we call the danger zone for steep deep - this basically means that some diamonds with this angle combo can leak light and look dark in some circumstances. But the best thing to do is to get an Idealscope image of diamonds with this combo as this will reveal whether there is any light leakage or not. A shallower pavilion angle may be a better fit for a 41 deg pav, but take each diamond on its own visual merits by further evaluation.

But as you have the diamond in your possession and love it, then that is the main thing and I am sure it is beautiful - nothing trumps your own eyes!

 

[stone-cold11]

What are you confused about?

HCA predicted a decrease in light return for this proportion, verified using an IS but is almost unnoticeable by normal human vision.

Note also that HCA just use the major dimensions of the RB, so alot of features it will miss. Maybe certain type of cuts, star, LGF appeals to you, they determine things light flashes fire. This is why you have to see a RB yourself after using HCA. It is for weeding out bad performers not to select best stones.

 

[agc]

Date: 10/5/2008 9:52:09 AM
Author: BCR
I am a little confused because of the following I found on GOG (not who I bought the stone from) and other places about HCA scores:

Diamonds with 41° pavilion angles (and even slightly over) are among the most beautifully cut diamonds in the world (when coupled with appropriate crown angles). Above we were examining how HCA scores got worse as leakage became more apparent when observed through red reflectors. According to both GIA and AGS laboratories (2 of the most renown and conservative labs in the world) the diamond in the above table with 35 degree crown angles and 41 degree pavilion angles (which gets a so-so HCA score of 2.2) consider this as a top grade and displays what is perhaps some of the best optics to be seen in round brilliant cut diamonds. In the above example the ever so faint amount of leakage in the center diamond and the diamond on the far right is impossible, I repeat, impossible to discern with human vision in any lighting environment you bring the diamond into. It is only something that can barely be seen under a red reflector and even at that it is still very difficult. Take this real diamond below as an example. It serves to demonstrate a few limitations of the HCA.

A 35/41 CA/PA combo does have slight leakage. A 34/41 combo does not have leakage. These combos are fine as long as there is superb optical symmetry otherwise there can be problems. This is why Garry deducts more harshly at 41 and above on the HCA. He has stated that diamonds with super symmetry can go to 2.5 on HCA especially with a little painting and be fine but you still need an IS image.