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How to calculate crown percentage?

sparkleandfire

Rough_Rock
Joined
Apr 19, 2019
Messages
63
Hello,
I have come across a stone but the crown percentage is not listed I have the table and total depth, is it possible to figure out the crown percentage from the table (58 ) and total depth (64.3). Thanks!
 

DejaWiz

Ideal_Rock
Joined
Apr 23, 2021
Messages
2,852
Pavilion depth plus girdle thickness, then subtract that from the overall depth.

Example:
Overall depth - 61.5%
Pavilion depth - 42.5%
Girdle thickness - 4%

42.5 + 4 = 46.5

61.5 - 46.5 = 15% crown height

Keep in mind that you'll be calculating off of averaged and rounded figures, so the result may not be dead on accurate.
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
17,675
Hello,
I have come across a stone but the crown percentage is not listed I have the table and total depth, is it possible to figure out the crown percentage from the table (58 ) and total depth (64.3). Thanks!

Crown % is unknowable for fancy shaped diamonds, but is a poor number to use anyway.
Crown height can easily be guestimated as high medium or low from videos.
 

oldminer

Ideal_Rock
Trade
Joined
Sep 3, 2000
Messages
6,643
Garry;
I think crown angle is possibly "unknowable" and what you meant to write above. With the rounded fancy shapes, crown angle often varies greatly from one place to the next. Crown height % of straight sided fancy shapes, such as emerald cut or princess cut, etc. is easily measured. Generally speaking, this is based on measurement taken at the width, just as total depth % is based on the relationship to the width of fancies or the average diameter of rounds.
 

Garry H (Cut Nut)

Super_Ideal_Rock
Trade
Joined
Aug 15, 2000
Messages
17,675
Garry;
I think crown angle is possibly "unknowable" and what you meant to write above. With the rounded fancy shapes, crown angle often varies greatly from one place to the next. Crown height % of straight sided fancy shapes, such as emerald cut or princess cut, etc. is easily measured. Generally speaking, this is based on measurement taken at the width, just as total depth % is based on the relationship to the width of fancies or the average diameter of rounds.

What I mean Dave is from just table and depth % crown Heights can only be guessed not known.
Until labs list crown and Pavilion % we are all in the dark.
 
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