New diamond

[Lazare000EX]

Hi all,

I recently bought a GIA triple excellent round brilliant diamond and would like to seek some advise from the pros. Below are the specs:-

Depth: 62%
Table: 57%
Crown angle: 35.5
Pavilion angle: 40.6
Star: 50%
LGF: 75%
HCA: 1.4
Fluorescence: None

No ASET/Ideal scope images. What do you guys think based on the specs alone? Anyone has a similar diamond with same specs?
Wondering if a LGF of 80% would perform better or a 75%

 

[YoLaL]

So far the proportions it's with in the requirements. 75% LG is better than 80%.
So I can say nothing to worry so much its pretty good proportions.
Would you mind sharing the C's please.

 

[BlingDreams]

Crown angle is a bit high, based on the ideal proportions (cutoff is 35). What do you think of the stone and it’s performance?

 

[Lazare000EX]

So far the proportions it's with in the requirements. 75% LG is better than 80%.
So I can say nothing to worry so much its pretty good proportions.
Would you mind sharing the C's please.

Thanks for your assurance. 0.64 F VS2

 

[Lazare000EX]

Crown angle is a bit high, based on the ideal proportions (cutoff is 35). What do you think of the stone and it’s performance?

Performance looks good to me. But most diamonds looks good in a B&M store. And without the scopes I can’t tell much that’s why I’m curious if anyone has a diamond with similar specs here

 

[BlingDreams]

You can buy an idealscope and H&A scope from amazon. That’s probably the route I’d take. You can also see if whiteflash has diamonds with the same parameters and look at those images for a general idea.

 

[YoLaL]

You are rigth it's a bit high, but its paired with a PA 40.6 . IRL if you compare this diamond to a CA 35 and PA 40.8 I can only say it's really hard to tell the differene if the symmetry are sharp.

Crown angle is a bit high, based on the ideal proportions (cutoff is 35). What do you think of the stone and it’s performance?

 

[Kaycee2018]

Performance looks good to me. But most diamonds looks good in a B&M store. And without the scopes I can’t tell much that’s why I’m curious if anyone has a diamond with similar specs here

The specs of my diamond (in my avatar) are very similar to this one and I am beyond thrilled with it's performance. Only H&A images were provided with mine. Bear in mind though that due to GIA's rounding, even diamonds with very similar specs can perform differently. Ideally you will be able to see the diamond in different lighting away from jewelry store lights to see how it truly performs. Your eyes are the real test. GL!

My spec are:

Depth: 61.9%
Table: 57%
Crown angle: 35
Pavilion angle: 40.6
Star: 50%
LGF: 75%
Crown: 15.5%
Pavilion: 42.5%
Girdle: Med-ST 3.5%

 

[Lazare000EX]

The specs of my diamond (in my avatar) are very similar to this one and I am beyond thrilled with it's performance. Only H&A images were provided with mine. Bear in mind though that due to GIA's rounding, even diamonds with very similar specs can perform differently. Ideally you will be able to see the diamond in different lighting away from jewelry store lights to see how it truly performs. Your eyes are the real test. GL!

My spec are:

Depth: 61.9%
Table: 57%
Crown angle: 35
Pavilion angle: 40.6
Star: 50%
LGF: 75%
Crown: 15.5%
Pavilion: 42.5%
Girdle: Med-ST 3.5%

Wow!! It’s a stunner!! Thanks so much for sharing! It’s a pity GIA rounds the numbers!

 

[Kaycee2018]

Wow!! It’s a stunner!! Thanks so much for sharing! It’s a pity GIA rounds the numbers!

Thank you! Yes...it's a real shame about GIA's rounding. But if you are willing to do the legwork and vetting, you can find GIA certified stones that perform wonderfully. I'm very happy with mine. Good luck to you!

 

[sledge]

A 35.5 crown paired with a 40.6 pavilion can work. It is pushing the normal bounds of what we prefer to see. The positive is that a big crown can throw lots of fire.

As @YoLaL started pointing out with his comparison of a 35.5/40.8 combo, it takes precise cutting & symmetry to make certain angles work. While always a factor, the minor facets (star & LGF's) become more critical as you push typical CA/PA combos as everything must play nicely together. While certain combos can work, sometimes it's best left in the hands of a super ideal vendor who better understands the precision required and that uses advanced AGS reporting with 3D modeling to confirm cut quality. Additionally, they also provide actual ASET, IS and H&A imaging of the specific stone in question to confirm it does all work.

As already touch on, one of the reasons we don't like to see a GIA stone that is pushing the boundaries is due to less precise 2D modeling combined with funky averaging & rounding of values. If you were to look at specific measurements, you may find that some are much better or worse than shown on the reports. For this reason, we recommend ASET or idealscope images so you can see if there is any angles that are out of whack enough that they cause a problem (light leakage).

In regards to 75 or 80 LGF's, both are acceptable. I prefer 75 LGF's as I like "fat arrows". However, 77 is the optimum value for the best H&A symmetry.

Also, we must take into account more GIA averaging that rounds to the nearest 5%. This means 73 LGF's could be reported as 75's, just as 77 LGF's could be reported as 75. Consequently a 78 LGF would be reported as 80, just as an 82 LGF would be reported as 80.

Generally speaking, 75-80% is acceptable. And assuming (massive assumption FYI) that a stone exhibits well performing proportions & excellent optical symmetry then a 75 LGF will perform better in dark environments and indirect lighting. An 80 LGF will perform better in very bright lighting conditions.

As evidenced below, an 80 LGF creates a thinner arrow and will create more, but smaller flashes, of sparkle sometimes called "pin-fire" flash. The fatter arrow from 75 LGF's will create less, but bolder flashes of light.

If you would like to read more about all this:
https://www.prosumerdiamonds.com/crown-angle/
https://www.prosumerdiamonds.com/lower-girdles/
https://www.whiteflash.com/about-diamonds/diamond-education/facets-the-lower-halves.htm
http://www.heartsandarrows.com/hearts-arrows-diamond-ideal-cut-dna.aspx
https://www.whiteflash.com/about-diamonds/diamond-education/facets-the-lower-halves.htm
https://www.pricescope.com/journal/do_pavilion_mains_drive_light_return_modern_round_brilliant

 

[Lazare000EX]

A 35.5 crown paired with a 40.6 pavilion can work. It is pushing the normal bounds of what we prefer to see. The positive is that a big crown can throw lots of fire.

As @YoLaL started pointing out with his comparison of a 35.5/40.8 combo, it takes precise cutting & symmetry to make certain angles work. While always a factor, the minor facets (star & LGF's) become more critical as you push typical CA/PA combos as everything must play nicely together. While certain combos can work, sometimes it's best left in the hands of a super ideal vendor who better understands the precision required and that uses advanced AGS reporting with 3D modeling to confirm cut quality. Additionally, they also provide actual ASET, IS and H&A imaging of the specific stone in question to confirm it does all work.

As already touch on, one of the reasons we don't like to see a GIA stone that is pushing the boundaries is due to less precise 2D modeling combined with funky averaging & rounding of values. If you were to look at specific measurements, you may find that some are much better or worse than shown on the reports. For this reason, we recommend ASET or idealscope images so you can see if there is any angles that are out of whack enough that they cause a problem (light leakage).

In regards to 75 or 80 LGF's, both are acceptable. I prefer 75 LGF's as I like "fat arrows". However, 77 is the optimum value for the best H&A symmetry.

Also, we must take into account more GIA averaging that rounds to the nearest 5%. This means 73 LGF's could be reported as 75's, just as 77 LGF's could be reported as 75. Consequently a 78 LGF would be reported as 80, just as an 82 LGF would be reported as 80.

Generally speaking, 75-80% is acceptable. And assuming (massive assumption FYI) that a stone exhibits well performing proportions & excellent optical symmetry then a 75 LGF will perform better in dark environments and indirect lighting. An 80 LGF will perform better in very bright lighting conditions.

As evidenced below, an 80 LGF creates a thinner arrow and will create more, but smaller flashes, of sparkle sometimes called "pin-fire" flash. The fatter arrow from 75 LGF's will create less, but bolder flashes of light.

If you would like to read more about all this:
https://www.prosumerdiamonds.com/crown-angle/
https://www.prosumerdiamonds.com/lower-girdles/
https://www.whiteflash.com/about-diamonds/diamond-education/facets-the-lower-halves.htm
http://www.heartsandarrows.com/hearts-arrows-diamond-ideal-cut-dna.aspx
https://www.whiteflash.com/about-diamonds/diamond-education/facets-the-lower-halves.htm
https://www.pricescope.com/journal/do_pavilion_mains_drive_light_return_modern_round_brilliant

Thanks for that detailed write up, sledge. I know 77% LGF is ideal, but which LGF works better for my combo?

 

[missyminx]

You can buy an idealscope and H&A scope from amazon. That’s probably the route I’d take. You can also see if whiteflash has diamonds with the same parameters and look at those images for a general idea.

Hi SG @Lazare000EX I have an idealscope and the ASET scope if you want to take those photos!

 

[Lazare000EX]

Hello @missyminx!!! I would really appreciate if you could lend me the scopes to take the photos!!

 

[missyminx]

Definitely could do, but not sure how we can get in touch because this board prohibits private messaging I think!

 

[Lazare000EX]

Do you have insta or something where I can PM u?

 

[Lazare000EX]

Definitely could do, but not sure how we can get in touch because this board prohibits private messaging I think!

@missyminx or you could text me at 81288738.