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 Crown and Pavilion Angles

P:  10/20/2008 3:51:15 PM  
tunis
tunis

Rough Rock
Total Posts: 66
Last Post: 12/4/2008
Member Since: 10/3/2008
 
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

 


Posted:  10/20/2008 3:51:15 PM

 There are 4 replies to this message.  There are 4 replies on this page.

P: 10/20/2008 3:58:29 PM
Garry H (Cut Nut)
Garry H (Cut Nut)

Ideal Rock
Total Posts: 11,586
Last Post: 11/25/2009
Member Since: 8/16/2000
 
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.

Garry Holloway FGAA DipDT

HCA and Ideal-scope developer

http://www.ideal-scope.com and
http://www.HollowayDiamonds.com.au

Posted:  10/20/2008 3:58:29 PM
P: 10/20/2008 9:51:18 PM
amyjokerette
amyjokerette

Cut Rock
Total Posts: 307
Last Post: 9/19/2009
Member Since: 9/5/2008
 
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.




AmyJokerette: Former maul store shopper... newly converted PS perfectionist!

Posted:  10/20/2008 9:51:18 PM
P: 10/20/2008 10:22:13 PM
neatfreak
neatfreak

Ideal Rock
Total Posts: 13,477
Last Post: 11/24/2009
Member Since: 2/17/2007
 
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!)

Posted:  10/20/2008 10:22:13 PM
P: 10/21/2008 7:20:14 AM
Ellen
Ellen

Ideal Rock
Total Posts: 22,894
Last Post: 11/6/2009
Member Since: 1/13/2006
 
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)."

~~~~~~~~~~~~~~~~

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Posted:  10/21/2008 7:20:14 AM

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