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Holloway Cut Adviser

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MissDimity

Shiny_Rock
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Oct 31, 2008
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Hi all,

My SO and I are going shopping for diamonds and I am now very familiar in using the HCA tool attached to this PS site. However, if I were to go and check out diamonds (through diamond merchant/ jeweler), is there a formula I can use using depth%, table%, crown angle, pavilion angle or crown % , pavillion %, measures, to calculate the score on the spot, rather than taking measures and then having to check them online.

Would appreciate any help on the matter? because otherwise I would be just going to the dealer and saying I want an excellent or ideal cut, however a score below 2 isn''t always reflected with "excellent" cut diamonds.
 

Lorelei

Super_Ideal_Rock
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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!
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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).

 

MissDimity

Shiny_Rock
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Oct 31, 2008
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209
Thanks for your prompt response and info, Lorelai !

That''s a good cheat sheet to have and is exactly the kind of details that I wanted to know, for what I should look out for.

Thanks again !
 

Lorelei

Super_Ideal_Rock
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Date: 11/18/2008 3:49:20 AM
Author: MissDimity
Thanks for your prompt response and info, Lorelai !

That''s a good cheat sheet to have and is exactly the kind of details that I wanted to know, for what I should look out for.

Thanks again !
You are most welcome, very glad to help you dear!
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Stone-cold11

Super_Ideal_Rock
Joined
Sep 9, 2008
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14,069
Date: 11/18/2008 3:41:45 AM
Author:MissDimity

Would appreciate any help on the matter? because otherwise I would be just going to the dealer and saying I want an excellent or ideal cut, however a score below 2 isn''t always reflected with ''excellent'' cut diamonds.

And a GIA excellent will not always score below a HCA 2.

HCA < 2 includes shallower crown/pavilion angle combinations that are classified as pendant/earring stone by Holloway, check out the usage and warning information. These will look dark when you view the stone too closely but perform well in normal viewing distances. If you find one in the store, check it out carefully and see if the stone lose it brilliance when you look at it closely.

Also check out what Holloway termed as the FIC and BIC cuts. These are away from the normal ideal cuts dimension, with BIC having less than 32.5 degrees crown angle and FIC greater than 35.5 degrees crown angle. BIC will look bigger and brighter for a given weight but less fire return. FIC will have more fire return but slightly smaller for a given weight and less brilliance return. These can also be of good value because they are class outside of ideal/excellent cuts thus you will pay less of a premium on the cuts when they still perform great.

Hope this helps.
 
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