Formula for calculating crown and pavillion angles

[diamondlil]

Hi all,




Could someone post the formula for calculating crown and pavillion angles from the percentages shown on EGL certs?

Assuming the percentages are accurate (I know some folks here are very wary of EGL as a whole), will the calculated angles be accurate enough to use on the HCA?




Thanks so much!




Diamondlil

 

[pqcollectibles]

Several attempts have been posted and tried, but they weren't totally accurate. The girdle thickness variances from diamond to diamond evidently affect the outcome of the mathmatical equations.

You can use the %'s in the HCA. Usually, the % score is about half the true number derived using angles.

 

[lara]

I'm sure that's usually true about the HCA score not being as good when you use the angles, but in my case it turned out exactly the same (when I finally did get the angles). 1.2 HCA both with % and angles.

 

[pqcollectibles]

Interesting, Lara. That has not been my experience at all. I've run all my diamonds using both %'s and angles. The %'s score ran about half the angles score on the larger diamond. My new diamond scores 1.3 using angles and 0.7 using %'s. My earrings both scored 0.9 using %'s and 1.2 using angles.

It would be great if you could post your angles and your %'s for us. When the question of mathematical formulas was posed a year ago, I ran a bunch of diamonds all 3 ways. Angles, %'s, and mathematical formula. I never got the %'s and formulas to match the angles. Your diamond specs would be interesting indeed!

 

[lara]

Hi, pq. Here's the #s.
t. depth, 58.5, table 59, crown 13%, pav 43%, crown angle 31.9, pav. angle 40.8. Med girdle.

 

[pqcollectibles]

WOW, Lara!!

That's KEWL!!

That's the first one I've seen like that!!

I haven't seen too many BIC's and FIC's either, tho.