Holloway Cut Adviser

Here are some numbers you can use, the cheat sheet that many PSers have used for some time now.  These won't calculate the HCA score but are very safe numbers you can use as a guideline to find a well cut stone.  If you have the numbers and some candidates which fit that you can see, then you can manage without the HCA.  Or if you wish, ask the jeweller if you can borrow his computer and run them through that way!

depth - 60 - 62% - although my personal preference is to 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

note - 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 - check as appropriate!

Also here are some good angle combos which might help from one of the experts.

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).

Nothing is more sacred as the bond between horse and rider...no other creature can ever become so emotionally close to a human as a horse. When a horse dies, the memory lives on because an enormous part of his owner's heart, soul, very existence dies also...but that can never be laid to rest, it is not meant to be...
- Stephanie M Thorn

HCA predates and out modes other earlier proportion based systems.

None should be seen as anyhting other than rejection tools.

None are now linear - so you can not get what you want in a simple form

Garry Holloway FGAA DipDT

HCA and Ideal-scope developer

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