Question on Girdle Thickness in Fancy Cut Diamonds

profile view of brown diamond

Profile View of Diamond

Question: I had been browsing diamonds online for quite some time now and intend to buy one in the next few weeks. During my research, I had noticed many diamonds exhibit girdle thickness that seem to vary quite wildly from each other.

For example, thin – medium girdle thicknesses are typically seen in round diamonds. We see a larger fluctuation in fancy cuts such as thin – extremely thick, medium – slightly thick, thick – extremely thick, thin to very thick and the list goes on for girdle thicknesses.

I had read in your article on diamond girdle sizes and you mentioned that medium is the one we should go for. Based on my fiancé’s preferences, I had been looking at some fancy cuts lately and had seen some pretty nice ones at James Allen. However, the concern I have is that some of these shortlisted diamonds have girdle thickness from thin – very thick or medium – extremely thick.

Should I discount these diamonds and only select those with a medium girdle?


Hi Dreamer,

You had raised quite a number of points here and I will attempt to answer them one by one. Typically, I would avoid diamonds with an extremely thick girdle as there is a possibility the girdle can act as an extra facet of sorts. In poorly cut diamond, this can alter the diamond’s appearance in a way which is unpleasant and distracting to look at.

Next, if a diamond has a uniform girdle of ‘extremely thick’, I would advise you to avoid them. Such diamonds are overweight and you are basically paying for the “dead weight” that you can’t see once it is mounted.

For fancy cuts, if a diamond exhibits a girdle of medium – extremely thick, I wouldn’t avoid it ‘per se’ without knowing the rest of the diamond’s properties. This should be determined on a case to case basis.


girdle thickness issues

Do you know how the girdle thickness is measured?

Basically, the girdle is measured around the entire circumference of the diamond. The thinnest and thickest areas will be listed in the grading report. In the example above, the girdle of the diamond is ‘medium’ at its thinnest point, and ‘extremely thick’ at its thickest point.

Now, I wouldn’t totally write off a diamond in this case as it might not be detrimental to the stone’s outlook. You will need further data like ASET images and videos to determine whether it is a keeper.

I would however, always avoid diamonds that fall under these scenarios:

1) Any mention of Extremely Thin.
2) A uniform girdle thickness of Extremely Thick.
3) Huge deviations like Very Thin – Extremely Thick.

Hope this helps clarify things,

When searching for fancy shaped diamonds, the odds are against you to buying a well-cut diamond. You need every tool at your disposal to make the best possible choices and I highly recommend because you can see exactly how the diamond looks like with their video technology. On top of that, they are able to perform gemological evaluations like light performance and capture ASET imagery on your behalf.

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