Bottom Line Recommendation:
Diamond Symmetry refers to how well aligned the facets of a diamond are. i.e., do the edges of the facets on the top and bottom of the diamond line up along the girdle? Are the facets aligned symmetrically around the diamond?
The simple answer to that question is: not really. Take a look at the diagram on the right. Each of the problems mentioned there (off-center culet, off-center table, misshapen facets, out-of-round circumference, crown and pavilion misalignment, and a wavy girdle) can definitely take away from the beauty of a diamond. That’s not the issue. The issue is that, I, the diamond expert with 6+ years of experience can hardly tell the difference between a diamond with “Good” symmetry and “Excellent” symmetry. You will only see noticeable defects in symmetry as found in the diagram to the right in diamonds with a “Fair” or “Poor” symmetry grade. So like Polish, do not spend any additional money to buy a diamond with a “Very Good” or “Excellent” symmetry grade.
If you have any questions, please post them in the comments below. I will usually respond within 24 hours.