presence or lack of a H&A pattern not a reliable indication as to the light return

[haagen_dazs]

I refer to Todd L. Gray''s 3rd post in this thread.
https://www.pricescope.com/community/threads/h-a-certificate-does-the-lab-make-a-big-difference.48961/

"The presence or lack of a H&A pattern is not a reliable indication as to the light return of the diamond, nor does it have a direct bearing on the color of the diamond. However, the proportions of the diamond AND the precision of the faceting and consistency of the angles that make up the high and low range that determines the average measurement of those angles that appears on the lab reports does have a direct effect on the potential light return of a diamond..."


I am still learning,
The 2nd part of the paragraph makes sense but I wanted to get some clarification on the first part.

I thought H&A = optical symmetry.
Doesn''t a optically cut help assist in return as much light as possible?
In order for the H&A to appear nicely when viewed by a person, doesn''t the tolerances for the facet angles have to be tight else the symmetry will be wonky or skewed?

If there are more resources on this topic regarding the first part of the paragraph, could someone point in the right direction?

It sounds like a SARIN report is pretty important based on the stand taken in the 2nd part pf the paragraph.

Are there examples of a diamond that lacks a H&A pattern and yet gives even better light return that a diamond that has one?

I am sure my logic/understanding is flawed in some ways hence these questions.

THANKS!!

 

[stone-cold11]

Optical symm is different from optical performance.

A stone can exhibit H&A symm/pattern but cut steep/deep or too shallow for optimal optical performance.

 

[Lula]

Hi, Haagen,
There was some good information provided by Stone, Garry and Rhino (Jonathan from Good old Gold) in this thread link
about optical symmetry that I started awhile ago.

 

[risingsun]

I would suggest these two tutorials from High Performance Diamonds. FYI, I did not purchase my diamond from them, but I think that their information is spot on. The first piece is on precision, which covers H&A and optical symmetry. From there you can click on the tutorial for performance, which discusses light performance. HTH.

http://highperformancediamonds.com/index.php?page=education-precision

http://highperformancediamonds.com/index.php?page=education-performance

 

[Lorelei]

Top optical symmetry is the result of how extremely precise cutting shows a hearts and arrows pattern due to the internal reflections in the stone.

The overall proportions plus the crown and pavilion angles in particular are the main engines driving the light return to result in a well cut and sparkly diamond.

Therefore you can have diamonds with superb proportions and top optical symmetry which have both top performance and optical symmetry/ h&a ( branded h&a) -

You can have a diamond with great proportions and optical symmetry showing a distinct but imperfect h&a pattern which some buy as they don't need the whole perfect h&a package, these can be lovely diamonds-

You can have diamonds with great proportions with mediocre optical symmetry so good performance and indistinct patterning-

I have seen some with a decent arrow pattern but not so great proportions too.