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Beyond The Four C's When Choosing


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i sort of understand the 4 c comparisons, but beyond that i get lost. are one of these numbers off clearly on paper?




grade report for stone:




what are the key %'s in the cut that will effect the stone's appearance? and what ranges should i be looking for? for example, here are 3 stones and some numbers...which is best on paper? soooooo confusing!


stones 1:


Table: 56%

Crown Angle: 34.5

Crown depth: 15%

Pavilion Angle: 40.6

Depth: 61.2%


stone 2:


Table: 55%

Crown Angle: 35.5

Crown depth: 16%

Pavilion Angle: 40.8

Depth: 62.6


stone 3:


Table: 60%

Crown Angle: 34

Crown depth: 13.5%

Pavilion Angle: 40.8

Depth: 60

Edited by stingyboy
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Generally speaking- if GIA gave it an EX cut grade, you'll be ok.

There are subtle differences between, say, a 57% table and a 60% table.

I'd suggest finding a store that carries well cut stones to see if you can find a way to see a few examples.

Some folks can see the slight difference, others can not.

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Those are all likely to be pretty good. The GIA ‘excellent’ grade means that a stone is in the top 20% on their scale. That’s not exactly an endorsement but it’s an improvement over where people were even 3 years ago in trying to buy a stone based solely on the lab exam.


The next step is to look at it, show it to your friends, neighbors and appraiser. Cut is one of those 4 C’s and it’s definitely the most difficult to wrap your mind around.



Edited by denverappraiser
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  • 2 months later...

Apart from the 4 Cs, the GIA report has graded Polish, Symmetry and Fluorescence. Please find a brief explanation for these.




Polish enhances the intensity of light reflected from, or refracted into and out of a diamond. Diamonds with poor polish are less brilliant because they have microscopic polish lines that blur the surface of the diamond. The polish lines are caused by minute diamond crystals which are embedded in the polishing wheels used by the diamond cutters to polish the surface of the diamond after cutting.




Symmetry refers to the alignment of the facets of a diamond. Symmetry reflects the exactness of the shape and arrangement of facets of the diamond. When a diamond is polished, it may be slightly off round, have variations in girdle thickness, tilting of the table, and off centering the table or the culet etc. To the unaided eye, the symmetry usually has little effect on appearance; a symmetrical flaw seems like pinpoint inclusions.




Fluorescence is an effect that is seen in some diamonds when they are exposed to long-wave ultraviolet light (such as the lighting frequently seen in dance clubs) or fluorescent light (such as the lighting frequently seen in a showroom). Under most lighting conditions, this fluorescence is not detectable to the eye. A diamond that has fluorescence has the tendency to emit soft colored glow when subjected to ultraviolet light. Diamonds with very strong fluorescence may appear to be less brilliant or even cloudy when exposed to UV lights. But such diamonds are very rare.


While most gemologists prefer diamonds without this effect, some people enjoy it. It is a matter of what appeals to the aesthetics.


Hope this is helpful.





Edited by Angara.com
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