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About A Diamond's Depth


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Hi everyone, I have just two quick questions regarding the depth of diamond. First, between pavillion depth and crown depth, which has a bigger effect on the performance of a diamond? Also, how a diamond would perform if its crown is cut slightly deeper than usual while its pavillion is perfectly cut with a normal value of depth? Thanks.

Edited by steelgrey330i
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More or less like a BMW with a slightly raised suspension and softer dampers than normal. More comfortable ride, but less sensitive to road conditions. :P


Sorry - couldn't resist.


It's difficult to answer your question, because terms such as "normal" and "slightly" are not precise enough. From Tolkowski's PhD thesis in the 1910s to modern GIA and AGS cut analysis, what is clear is that there isn't one single set of proportions that provides good light return, but rather all parameters work together to make a stone beautiful (or not). Would you consider 1% "slightly"? Some people will tell you that a 59% table is still good, but a 60% table is too much. A rigid formula-based approach to diamond proportions is likely to result in many beautiful stones being discarded (or conversely in many ugly ones being accepted).


Are you looking at a particular stone?

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Sounds like you are a fan of bmw too, haha. Actually, I am looking at a stone with GIA rated as excellent cut and here are the specs and maybe you and other professionals can give me some comments.

0.9 carats


E color VVS2

ex polish and symmetry


crown angle: 36.5 degree

crown depth: 16.5%

pavillion angle: 41 degree

pavillion depth: 43%

overall depth: 63.2 %

girdle: thin to medium faceted

As you can see from the specs, the extra depth is caused by the crown depth and also the 36.5 degree crown angle is definitely on the large side. So I want to know how will that extra depth and large crown angle will effect the performance of this diamond. Thanks.

Edited by steelgrey330i
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Well, a semi-educated guess would say that you are going to get a lot of sparkle and refracted (coloured) light, but not as much white (reflected) light as other stones with a less steep crown and a larger table. But it's a guess based on the laws of optics and it assumes that the stone is perfect in all other respects. Many subtle details of cut are not captured by stats on a GIA report; some would find a brilliancescope report or ASET image useful (and others would think it's a waste of time).


There's no substitute for a pair of - preferably expert - eyes. Can the dealer who has the stone tell you something about it? Even better, can he/she show it to you, with other stones to compare to?


Given the specs of the stone you are considering, one thing I'd look at would be comparing that stone to others with clarity down two or even three notches (VS or SI1), and looking at F, G or even H colour stones, either flexing your budget downwards or going for a larger stone. I'm not suggesting you necessarily do either thing, but to get an idea of the trade-offs that you are facing. If you have already done your homework in this respect, and are set on those colour/clarity grades, there is not much else to do apart from looking at the stones themselves

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