Crown and pavilion calculation

[glaucomflecken]

hi! this is a longshot but...

is there any way to figure out the crown and pavilion angles of a stone without the sarin analysis? i got my stone before we found this site and learned about all this. My stone is GIA, so i dont have any of that info, only table,depth, etc. my stone is beautiful but i''m always curious what these numbers are since everyone here says they are the most critical in determining how ideal the cut is

thanks

 

[Garry H (Cut Nut)]

Not once it is set and not without a sarin scan

But you can examine it with an ideal-scope which will tell you more than the scan info anyway

 

[diamond island]

Is the ideal scope the same or similar or gives you the same information as the Firescope used to sell the eightstar?

 

[Garry H (Cut Nut)]

Yes.

I have had a Firescope for 20 years.

 

[asblackrock]

For round brilliant cut diamonds I have worked out a formula for calculating crown and pav angles if you have crown height and pav depth (see: An easy way of calculating crown and pavilion angles ). The only problem is that figures for crown height and pav depth are apparently rounded off to the nearest whole number, so results are only approximate. A GIA certificate will unfortunately not give you any of this info though.

PS The name glaucomflecken caught my attention. Is there an optometric/ophthalmological connection?

 

[Nicrez]

There are actually methods that can help you determine the angles, or approximate them. There is a semi-mathematical way to determine it, but to do so would be a bit complex, and I would have to explain some ways of finding OTHER information about your stone first. When i get a chance, I will try to post the method later...

You could always take it to a gemologist, and they could literally eyeball it and let you know the approximations in a few minutes.

 

[glaucomflecken]

Thanks everyone. My stone is really sparkly so I will assume those proportions are ideal

Angela:
You are correct, I am an optometrist. my friends and i in school thought glaucomflecken was a fun word to say (although a serious eye condition). i''m a nerd.

 

[Garry H (Cut Nut)]

Date: 11/11/2004 8:17:34 AM
Author: Nicrez

There are actually methods that can help you determine the angles, or approximate them. There is a semi-mathematical way to determine it, but to do so would be a bit complex, and I would have to explain some ways of finding OTHER information about your stone first. When i get a chance, I will try to post the method later...

You could always take it to a gemologist, and they could literally eyeball it and let you know the approximations in a few minutes.

Nicrez you may have learned, or will be taught the Liddicaot Rapid Sight Pavilion Depth Estimation method.

I am afraid to tell you, it has errors and should not be used.

In your library your GIA library can get http://www.austgem.gil.com.au/ab21-10.html and learn about it.

I doubt your lecturers will want to know about it though.

The rapid sight system is what led the industry to use pavilion depth % as a measure of cut quality. This is a great pity because people assume a correlation between pavilion depth and pavilion angle. They almost always get a lower angle than it actually is, and this is very bad because as we know the difference between 40.9 and 41.1 is rather large in cut quality.

So Angela, I strongly advise you do not propagate the math method because depth % is almost always understated by scanners.

 

[JohnQuixote]

Date: 11/11/2004 2:29 PM
Author: Garry H (Cut Nut)

Nicrez you may have learned, or will be taught the Liddicaot Rapid Sight Pavilion Depth Estimation method.

(Aside: I'll bet we never expected to see that and "glaucomflecken" in the same thread...)

 

[glaucomflecken]

Date: 11/11/2004 8:12:35 PM
Author: JohnQuixote

Date: 11/11/2004 2:29 PM

Author: Garry H (Cut Nut)

Nicrez you may have learned, or will be taught the Liddicaot Rapid Sight Pavilion Depth Estimation method.

(Aside: I'll bet we never expected to see that and 'glaucomflecken' in the same thread...)