When polishing a rough diamond the aim is to cut the heaviest, most valuable diamond possible. This often means polishing a diamond with imperfect symmetry to avoid inclusions or just to achieve a "magic weight" (like 1.00ct). The polished diamond may be slightly off round, have variations in girdle thickness, tilting of the table, and off centering the table or the culet etc. Contrary to popular belief, symmetry defects in a diamond are often the result of a highly skilled cutter, rather than an indication of poor skills.
The diamond images we have used in this tutorial are mostly symmetrical. But in the real world very few diamonds are perfectly symmetrical, but symmetry is less important to the overall beauty of a diamond than the critical facet proportions. You may never notice any difference between diamonds with Ideal, Excellent Very Good or even some Good symmetry diamonds.
|Price difference for Round diamonds
1-1.49ct, F-H, VS1-SI2, GIA and AGS
58%-63% Depth, 53%-58% Table
Data for April, 2004
|Polish & Symmetry||% Price difference|
|Ex/Ex or Id/Id||0%|
|Ex/VG or Id/VG||-6.5%|
The Ideal-Scope reference chart is an effective way to judge symmetry because the patterns we observe with it display "optical" symmetry. Another category of high symmetry diamonds is Hearts and Arrows.
Diamond with GIA good symmetry
Diamond with AGS ideal symmetry