Crown and Pavilion Angles

[tunis]

Can someone give me an idea of what the optimal crown and pavilion angles might be? My sense is something on the order of 34-35 for the crown and 40.5-41 for the pavilion but is there such thing as a sweet spot within this sweet zone?

Thanks in advance,

Tunis

 

[Garry H (Cut Nut)]

There is a sweet range.
Your approach is grossly misguided by many consumer here.
If you like the sweet spot in the midddle of that range then you can very safely add 1/2 a degree to the pavilion if you subtract 2.5 degrees from the crown angle.
You can subtract 1/2 a degree and add 2.5 degrees to the crown as loong as the table size is 55% or less.

 

[amyjokerette]

Garry do you know how I can calculate or measure my crown and pavilion angles on my Leo diamond? They are not listed! I dont think they list them on the IGI certs... (sigh)
Not that it is a bi deal, I love my diamond... I was just curious if there was a formula or a way to measure it by taking a large photo or something.
Sorry to piggyback on this thread.

 

[neatfreak]

Garry of course is correct that there are many variations. To be super safe and make it easy, these parameters are good ones to start with:

depth - 60 - 62% - although you can allow up to 62.4%
table - 54- 57%
crown angle - 34- 35 degrees
pavilion angle - 40.6- 41 degrees
girdle - avoid extremes, look for thin to slightly thick, thin to medium etc
polish and symmetry - very good and above

with crown and pavilion angles at the shallower ends ( CA 34- PA 40.6) and steeper ( CA 35- PA 41) check to make sure these angles complement in that particular diamond - eyeballs, Idealscope, trusted vendor input (courtesy of Lorelei!)

 

[Ellen]

Here's a bit of a cheat sheet for GIA stones.

"With that said, here's a "Cliff's Notes" for staying near Tolkowsky/ideal angles with GIA reports (their numbers are rounded): A crown angle of 34.0, 34.5 or 35.0 is usually safe with a 40.8 pavilion angle. If pavilion angle = 40.6 lean toward a 34.5-35.0 crown. If pavilion angle = 41 lean toward a 34.0-34.5 crown.

GIA "EX" in cut is great at its heart, but it ranges a bit wider than some people prefer, particularly in deep combinations (pavilion > 41 with crown > 35)."