Help!! (with Angles - 2.6 RB)

[Tinky]

Hello. Can someone please give me the range (for which to stay within) of excellent/ideal crown and pavilion angles required for optimum Diamond performance? I understand even if a stone is graded GIA XXX that the angles still might not be optimal. I am looking at this B&M stone and someone on this site questioned its 36° crown angle. How will the steeper angle affect the stone's performance? Anyone? Note - I have seen the stone in person and (I am no expert ) it was very sparkly and showed rainbow colors. I took it outside of the store into the sunlight, I took it to different parts of the store under different lighting and it was really sparkly and fiery. What if I purchase this stone and get it home under different lighting and it doesnt sparkle as well. I don't know what to do.

The stone scored ALL 1A's except for a 2B on the crown angle on David Atlas' cut grade tool giving it a total score of 1B. Then I entered the numbers on the HCA tool and it scored a 3.6 very good.

All advice is appreciated.

GIA XXX RB Specs:
Total depth.........62.0%
Table size...........57%
Crown angle........36.0 deg.
Crown height.......15.5%
Pavilion angle......40.8 deg.
Pavilion depth .....43.0%
Star length..........50%
Lower half...........80%
Girdle................Med. to slightly thick, faceted (3.5%)
Culet.................None
Polish................Excellent
Symmetry...........Excellent
Fluorescence.......None

 

[MissElizabeth]

According to tyty333, these are some general guidelines for RB proportions:

depth - 60-62%
table - 54-57%
crown - 34-35 degrees
pavilion - 40.6 - 41.0 degrees

generally, you want to look for an HCA below 2.0, so I would get an Idealscope image of this diamond to determine it's light performance.

 

[Christina...]

First, I wouldn't purchase a stone without a really good return policy. Two your eyes are going to be the best judge of the diamonds beauty, but typically problems with steep/deep type stones are dark areas under the table. Did the stone appear bright from edge to edge when you viewed it, or did you notice any darkening under the table. I personally like a stone with a high crown and if the PA was 40.5-40.6 it would be the type of stone I lust after.

I'm assuming that you are unable to get IS images of the diamond. Is it possible for you to purchase one and then go back and take a look?