By now, you probably read or heard some stuff about the importance of symmetry grading and its impact on a diamond’s beauty. Very often, I receive emails from people seeking my opinion on the kind of symmetry grading they should look out for.
Should they consider only stones with excellent symmetry? Is a very good rating good enough? Is it necessary to buy a diamond with excellent symmetry to get the most beautiful stone?
Well, the answer to the above questions is: It depends.
To the lay person, the differences between a very good and excellent symmetry rating are usually not discernible by the naked eye. Unless you use a 10X loupe to inspect the diamond and know exactly where to look, you probably can’t tell the differences.
After all, isn’t symmetry all about lining up the individual facets precisely to each other? Logical thinking would probably tell us that precise facet alignments would yield a diamond with better light return.
That’s a HUGE MISCONCEPTION!
The truth is, light performance is heavily influenced by the diamond’s crown angles, pavilion angles, table size and depth. Even if a diamond achieves excellent symmetry and polish, it can still appear lifeless and dull if the crucial proportions are cut wrongly. Vice versa, if a diamond has only very good symmetry or good polish, it is still possible for it to appear brilliant and desirable.
0.70 Carat – G Color – SI2 Clarity – Dismal Looking Round Diamond
If you only had a photograph of the diamond for viewing without any further data, would you have thought that GIA assigned excellent ratings for both polish and symmetry? This sorry-looking diamond was cut to extremely poor proportions and received only a “good” cut grade by GIA.
0.70 Carat – I Color – VS2 Clarity – Excellent Cut Round Diamond
In comparison, this diamond only received a “very good” rating for its symmetry grade. Yet, it looks a thousand times better than the first stone. The second diamond received an overall cut rating of “excellent” from GIA and I am sure you know which is the hands down winner if you compare these 2 stones side by side.
In this case, excellent cut, polish and symmetry are “prerequisites” if you are considering to buy hearts and arrows diamonds. In order to achieve a beautiful patterning, the proportions and angles of each individual facet must be extremely precise. A little deviation in cutting proportions would result in undesirable effects on the diamond’s optical symmetry (h&a patterning).
Also, I want to bring to your attention that NOT every diamond with GIA triple excellent or AGS triple ideal ratings would automatically qualify it as a hearts and arrows diamond. The following excerpt from GIA’s Symmetry Grading Boundaries For Round Brilliant Cut Diamonds, shows you the degree of “tolerances” used in their grading system.
Everyone wants to excel and be the best they can be. Diamonds are no different. Cutters and buyers around the world perceive a super ideal hearts and arrows diamond to be analogous to winning a gold medal in the Olympics. Very few can actually win it and stake claim to be the best.
In order for a diamond to achieve picture perfect hearts and arrows patterning, it requires all of the proportion factors to be stricter than those acceptable for an excellent rating. For example, a round brilliant cut with table size variation of 1.0%, culet off center by 0.5% and table off-center by 0.4% will NOT result in nice looking H&A patterns.
This diamond was graded with ideal symmetry by AGS but it doesn’t possess ideal optical symmetry.
You can see the obvious twisting and deformation of the hearts in the image above.
As with everything else, a higher quality product is usually more expensive. To achieve such a level of cut precision, skilled labor is required and more material needs to be removed from the rough diamond during polishing.
So, the question you need to ask yourself is whether this increase in price is justifiable for a slight difference in light performance. Ultimately, buying diamonds is a matter of personal preferences and what really matters is that you enjoy your purchase. If you are a perfectionist, by all means go ahead and get the diamond with the best finishing.<< Prev Page