About Polish & Symmetry


Jul 18, 2011
There's so much information on this site. If I searched enough, I'm sure I could find this covered plenty of times. But you guys always seem so helpful and quick to respond to questions, so I figured I would just post my query here.

I'm wondering what the realistic effect of Polish and Symmetry is on the performance of a round brilliant diamond. I was curious about a .96ct GIA graded stone that comes in at VG cut, H color, VS2 clarity. Based on the GIA report, its dimensions score it a 0.7 on the HCA and a 1A score in the AGA cut class tool. The only real knock against it is the "Very Good" symmetry and "Good" polish.

So my question is: how much does it matter? Sure, I would prefer an Excellent cut with Ex polish and symmetry. But I feel like the price is pretty good on this one.

The retailer's rep responded with this:

We generally do not recommend Good polish in a round diamond (or VG cut) unless the budget makes it unavoidable and the customer expresses that size or color are more important that overall appearance (brightness, sparkle).

Typically, in these situations, an SI1 diamond with Excellent cut is a better option since it improves the overall appearance, while making no visible sacrifice in clarity.

And in this case, since Polish is the questionable value, why would a retailer not send this to be cleaned up with a better polish? How much would it cost me to have someone polish it? It seems like it would add literally 20% to the value of the stone (as compared to similar ones with better symm/polish rating).


Sep 9, 2008
Probably the graining or an inclusions is preventing the stone from getting a better polish grade.


Sep 3, 2000
The way the diamond has formed in nature may make it less able to be polished and faceted exactly as the cutter might wish. Diamond is so hard a material that when a sort of "twist" exists in the rough crystal, the cutter has less ability to shape the finished diamond to "Excellent" poish or symmetry. It may be a beautiful diamond at a great price and may give very high light return. It might not look as good as some more prefectly fashioned diamonds but without a direct comparison, side-by-side, you won't know for certain with any of our various parametric comparison tools. It could be a great buy and deserves a closer look and some comparison shopping.
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