Big different btw Excellent & Very good polish/symmetry?

[Samara83]

I have decided on an excellent cut round brilliant. The ones I have found that fit my price range, however, have "very good" polish & symmetry as opposed to "excellent". Is there a big difference? Or is this something that I would only notice under a microscope?

 

[Lorelei]

Date: 5/24/2010 12:10:16 PM
Author:Samara83
I have decided on an excellent cut round brilliant. The ones I have found that fit my price range, however, have ''very good'' polish & symmetry as opposed to ''excellent''. Is there a big difference? Or is this something that I would only notice under a microscope?

Hi Samara

There isn''t normally a visible difference to the naked untrained eye between very good polish and symmetry and above. More important are the overall proportions of the diamond as these have a greater impact on beauty and light return.

 

[FB.]

Very good polish is indistinguishable from Excellent polish. I'm happy to buy stones with VG polish.

Often, Very good symmetry and Excellent symmetry are difficult to tell apart unless you look very closely. In fancy shapes (e.g. pear shape), you can drop to Good symmetry and not notice a difference. With rounds, I prefer Excellent symmetry. Although it is a subjective decision, a round stone with good angles and excellent symmetry usually outperforms a stone with very good symmetry, due to more perfect alignment of the facets. H&A is the classic definition of perfect symmetry. Not all stones with Excellent symmetry are good enough to qualify for H&A.
After seeing a few horrors in VG symmetry round stones that "on paper" should have been beautiful, I now only accept Ex symmetry in rounds. Basically; the less symmetrical, the less exact the angles will be. Yes, there are always exceptions which I'm sure someone will use to explain why they think that VG is as good as Ex.

 

[John P]

Date: 5/24/2010 1:17:14 PM
Author: FB.
Very good polish is indistinguishable from Excellent polish. I'm happy to buy stones with VG polish.

Often, Very good symmetry and Excellent symmetry are difficult to tell apart unless you look very closely. In fancy shapes (e.g. pear shape), you can drop to Good symmetry and not notice a difference. With rounds, I prefer Excellent symmetry. Although it is a subjective decision, a round stone with good angles and excellent symmetry usually outperforms a stone with very good symmetry, due to more perfect alignment of the facets. H&A is the classic definition of perfect symmetry. Not all stones with Excellent symmetry are good enough to qualify for H&A. After seeing a few horrors in VG symmetry round stones that 'on paper' should have been beautiful, I now only accept Ex symmetry in rounds. Basically; the less symmetrical, the less exact the angles will be. Yes, there are always exceptions which I'm sure someone will use to explain why they think that VG is as good as Ex.

Good answers to the topic's main question by the previous posters.

Forgive my OCD with the first red sentence: "Symmetry" as used on grading reports has nothing to do with 3D cut precision; required for H&A. I'm with you, as some people say "symmetry" to flip-flop between finish-sym, physical sym or optical-sym according to the conversation... But I'm afraid that tendency doesn't help clear communication, even amongst professionals.

The second red sentence is 100% right. Diamonds with EX finish-symmetry may or may not have the 3D cut precision required to show H&A. Furthermore, diamonds with less than EX finish-symmetry may show H&A, although the former case is more likely as a by-product of care taken in the crafting process.

These three examples all have EX or better symmetry grades, but different levels of 3D cut-precision - for which GIA and AGS reports don't give a judgment.

Original thread: https://www.pricescope.com/community/threads/images-of-h-a-vs-non-h-a-stones.74204/