Just like polish also symmetry does influence the beauty of a diamond. Symmetry describes
the alignment of the facets and the structure of the diamond.
A symmetrical appear of the diamond guarantees an equal distribution of brilliance and fire. Although most round brilliants are round by definition an asymmetrical form or imbalance can severely affect a diamond´s beauty in all diamond shapes.
The possible negative affect becomes obvious when considering a heart shape diamond with one of the shoulders (sides) being cut more prominent than the other which spoils the appearance all together. Diamonds are not always polished to perfect proportions and symmetry in order to retain as much weight – and therefore value – as possible but instead to achieve the best possible compromise of the two.
Usually round brilliants are symmetrical. The ideal would be an octagonal, perfectly centered table, perfectly round outline and having all facets properly aligned and in the right form. However, this ideal does not always match reality. Once again we need to recall that diamonds are a product of nature and every diamond polisher can only do as much as the stone itself has to offer in its rough state.
Most symmetry features are not critical for a diamond´s beauty. Benchmark for the evaluation of the symmetry is also the 10x magnifying loupe. Grading symmetry it is important to differentiate between minor and major symmetry faults, the latter of which do affect the appearance of the gem stone in total.
Facets do not meet or are misshapen
Table is not octagonal
Girdle outline being slightly out of round
Slightly off-center culet or table
Slightly wavy girdle
Major symmetry flaws:
Girdle out of round noticeable with the naked eye
The naked eye can observe the table not being parallel to the girdle
Obvious off-center table or culet
Obvious wavy girdle (very thin to very thick)
At 10x magnification symmetry features are not or only very difficult to see.
There are some subtle symmetry deviations that are visible under 10x magnification but not noticeable to the naked eye.
Several symmetry flaws are given and more prominent than at the symmetry grade very good. In some cases the brilliance can be affected.
Obvious symmetry deviations under 10x magnification may be seen by the naked eye.
Several major symmetry flaws that are also visible to the naked eye and that affect the diamond´s brilliance and fire.
Hearts and Arrows
An indicator for excellent symmetry is the so called “hearts and arrows” pattern that can be seen using the “Hearts and Arrows Scope”. Not all diamonds with excellent cut show this pattern, however, the differences within the range of an excellent cut cannot be noticed by the naked eye. In other words: Observing hearts and arrows may relate to excellent symmetry, yet it does not serve as evidence for an excellent overall cut grade itself.
An excellent cut with the hearts and arrows pattern does not mean the diamond is of superior quality or shows more sparkle. That is why GIA does not grade hearts and arrows as a special feature. Yet, sometimes GIA certificates can contain a comment of “H&A” or “hearts and arrows” if there is a laser inscription of this label – prior to the grading by the GIA laboratory.