If two different stones score 2.3 on HCA....

[sarah95]

and one is an EGL "excellent" cut and the other is a GIA excellent cut, will they both have the same amount of brilliance, or can the GIA stone still be better than the EGL one? I think this might be a stupid question, but I''m just wondering if both stones get the same exact results, will their performance be the same? I know diamonds are unique like snowflakes, so maybe my question just doesn''t make sense....

 

[:)]

It isn''t that GIA did the report or EGL did the report - it is the accuracy of grading (color, clarity, etc) that is sometimes/often an issue. The HCA is designed to help you weed out (not compare) stones that you cannot see with your eyes first. Equivalent HCA scores do not mean they will perform the same, so yes one stone could still be a better performer than the other.

Do you have specific stones/reports in mind? You could post the specs if you do.

 

[John P]

Date: 8/27/2008 4:56:39 PM
Author:sarah95
and one is an EGL 'excellent' cut and the other is a GIA excellent cut, will they both have the same amount of brilliance, or can the GIA stone still be better than the EGL one? I think this might be a stupid question, but I'm just wondering if both stones get the same exact results, will their performance be the same? I know diamonds are unique like snowflakes, so maybe my question just doesn't make sense....

When it comes to performance the HCA score is based on an imaginary outline of the diamond. This is enough to know weight to spread ratio and whether the angles will effectively return light in the big picture, but the amount of detail is limited - kind of like the chalk outline around a body (forgive the crude comparison). You need to fill in more information in order to accurately predict specifics.

Two diamonds at 2.3 might have equal light return or could perform differently than each other depending on optical symmetry, brillianteering variations and minor facets; especially lower halves. An ideal-scope and ASET image will reveal a lot about these things. The HCA just gives you the chalk outline.

 

[diagem]

Date: 8/27/2008 5:11:31 PM
Author: John Pollard

Date: 8/27/2008 4:56:39 PM
Author:sarah95
and one is an EGL ''excellent'' cut and the other is a GIA excellent cut, will they both have the same amount of brilliance, or can the GIA stone still be better than the EGL one? I think this might be a stupid question, but I''m just wondering if both stones get the same exact results, will their performance be the same? I know diamonds are unique like snowflakes, so maybe my question just doesn''t make sense....

When it comes to performance the HCA score is based on an imaginary outline of the diamond. This is enough to know weight to spread ratio and whether the angles will effectively return light in the big picture, but the amount of detail is limited - kind of like the chalk outline around a body (forgive the crude comparison). You need to fill in more information in order to accurately predict specifics.

Two diamonds at 2.3 might have equal light return or could perform differently than each other depending on optical symmetry, brillianteering variations and minor facets; especially lower halves. An ideal-scope and ASET image will reveal a lot about these things. The HCA just gives you the chalk outline.

I would assume it would still have significant weight as to who and what devices were used to exact measure the facet angles??
I mean..., the numbers on the lab reports are the ones you input into HCA? Correct?

 

[John P]

Date: 8/27/2008 5:19:41 PM
Author: DiaGem

Date: 8/27/2008 5:11:31 PM
Author: John Pollard

Date: 8/27/2008 4:56:39 PM
Author:sarah95
and one is an EGL 'excellent' cut and the other is a GIA excellent cut, will they both have the same amount of brilliance, or can the GIA stone still be better than the EGL one? I think this might be a stupid question, but I'm just wondering if both stones get the same exact results, will their performance be the same? I know diamonds are unique like snowflakes, so maybe my question just doesn't make sense....

When it comes to performance the HCA score is based on an imaginary outline of the diamond. This is enough to know weight to spread ratio and whether the angles will effectively return light in the big picture, but the amount of detail is limited - kind of like the chalk outline around a body (forgive the crude comparison). You need to fill in more information in order to accurately predict specifics.

Two diamonds at 2.3 might have equal light return or could perform differently than each other depending on optical symmetry, brillianteering variations and minor facets; especially lower halves. An ideal-scope and ASET image will reveal a lot about these things. The HCA just gives you the chalk outline.

I would assume it would still have significant weight as to who and what devices were used to exact measure the facet angles??
I mean..., the numbers on the lab reports are the ones you input into HCA? Correct?

Right, but the HCA results would not be impacted unless someone's machine is out of whack. Can you tell the difference between a 40.7 and a 40.8 pavilion with your naked eye?

For that matter GIA rounds some of their reported numbers. They maintain that a difference of a half-degree in avg crown angle is not visibly significant (arguable). Regardless...today's scan acuracy is well inside that tolerance and good enough for a meaningful HCA estimate. Just don't try to overinterpret the results. There are a lot of elements that are not included.