Shallow crown angle, good HCA score? What should I look for?

[jambo1981]

Hi,

I am looking at a stone that I love and looks beautiful. My questions is as follows:

This stone is a GIA triple ex, is a good price, and scores well on the HCA 1.7. The crown angle is way outside the figures people speak about as being ideal. It really does sparkle though, is there anything i should be worried about with a shallow angle and what if anything should i look out for when I view the stone? I can't get images sorry.

Spec:

0.72 E SI1 exexex 5.80x5.83x3.53 HCA 1.7 - No inclusions visible to naked eye and very very hard to spot with loupe (its a twinning wisp)
Depth: 60.8%
Table: 56%
Crown Angle: 32.5°
Crown Height: 14.0%
Pavilion Angle: 41.2°
Pavilion Depth: 43.5%
Star Length: 50%
Lower Half: 80%
Girdle: Medium to Slightly Thick, Faceted (3.5%)
Culet: None

Thanks

 

[John P]

Re: Shallow crown angle, good HCA score? What should I look

There is some give and take when it comes to complimentary proportions: The average crown angle can be slightly shallow as long as the table size permits proper crown height and the average pavilion angle is slightly deeper. 56/32.5/41.2 does work in that sense. It will have greater brightness and less visible fire in the balance of its performance qualities. It's predicted to receive AGS 1 in light performance, depending on cut consistency, precision and indexing.

To reach any conclusions I would want to know how consistently/precisely it was cut. 41.2 is a pavilion angle that's over some experts' tolerances. If too many of the individual facets are above that given average (the number represents eight measurements) there could be zones of leakage. An Ideal-Scope or ASET image would help in making that assessment here. It sounds like you've seen it, so you have the advantage over any internet-input.

As for what you should look for: You probably know that showroom lights make everything sparkle. Be sure to check it through a broad range of lighting conditions, including natural daylight and indirect lighting; hold it under the counter where no direct light can reach it. If the diamond still looks the same size and continues to have both white and colored flashes in its suite of visible performance (with the exception of diffused/fluorescent light where fire is reduced in any diamond) then you have your answers.

 

[jambo1981]

Re: Shallow crown angle, good HCA score? What should I look

thanks very much, still looked good in multiple light conditions so i've pulled the trigger

 

[yssie]

Re: Shallow crown angle, good HCA score? What should I look

What setting are you thinking of?