Note: This page talks about diamond cut and not diamond shape. Sometimes you will see the two terms used interchangeably but they are totally different concepts. Visit my Diamond Shapes page for more information on diamond shapes .
Diamond cut is the single most important parameter that effects how your diamond looks to the naked eye
- A GIA cut grade of “Very Good” is a great selection and offers a great sparkle. If you are looking for maximum brilliance you should consider getting the higher grade of “Excellent”. Unlike some minor upgrades (diamond color) going from Very Good to Excellent will offer a noticeable change.
- Vendors will often push for AGS Triple Zero or Triple Excellent grading from AGS. In almost all cases this is overkill and will not offer a noticeable improvement over AGS Very Good grading. In keeping with my philosophy of paying for what you can see I don’t recommend upgrading to the Triple Zero.
- Beware the independent diamond cut evaluation of online vendors for round diamonds- I have seen many online vendors list diamonds as Ideal but when checking the actual GIA or AGS certificate found that in fact they were not Ideal.
A diamond cut refers to the proportions of the parts of the diamond and how well the diamond reflects light. You know that sparkle that you see when looking at a diamond? Ever wonder why some diamonds sparkle more then others (you may see this referred to as diamond Brilliance). Almost always this is due to the quality diamond cut. The light or sparkle that you are seeing is the reflection of light off the diamonds table (technically there is more then one type of reflection that make up what you see and if you want a more technical understanding see this James Allen page on diamond cut). 9 times out of 10 a diamond that just doesn’t sparkle and has a bland look to it has a bad cut. Of all the 4 Cs, diamond cut is the one that has the greatest effect on the look of the diamond to the naked eye. A drop from VS1 to SI1 clarity or a E to H color is almost never noticeable however a drop from Ideal to Good will often times be noticeable to the naked eye because it will lack the sparkle one would expect.
The diamond cut is made up of a set of proportions including the diamonds diameter, table, and crown. In total there are 7 measurements that contribute to the cut but the 2 most important are table and depth. The table is the large polished part of the diamond that faces up and the depth is the total. The most basic rule of thumb when looking for a round diamond with a good cut is the “60/60” rule. What this rule states (its really more of a general guideline than a rule) is that you should look for a diamond with a table of 60% and a depth of 60%.
Each diamond shape has its own proportions that are considered best but round diamonds are the only ones that are defined on the diamond certification. In fact, until 2006 AGS was the only agency that had a set diamond cut grading system. In January of 2006 the GIA also introduced its own diamond cut grades and now both GIA and AGS offer diamond cut on their certificates. Unlike the 60/60 rule of thumb I mentioned above, the GIA and AGS diamond cut grading systems takes into the total proportions of the diamond and may give a diamond an Ideal grade even one of its parameters may be slightly higher or lower then what one would normally consider Ideal if another proportion compensates for this. (AGS doesn’t even give a 60/60 diamond its highest grade). Basically both AGS and GIA allow for mixing it up a little more then they used too and rely on actual return of light measurements rather then hard numbers.
To sum it up while I often recommend going with the lowest diamond clarity or diamond color that you can ,when it comes to cut I would recommend spending more for the better quality and going for the highest you can afford.
Note: Buying a diamond can be a nerve-racking experience. If you want my expert advice on buying the best diamond just drop me a note and tell me what you are looking for and how much you want to spend and I will get back to you with my personal recommendations for a beautiful stone that fits in your budget. This is a FREE service, doesn’t cost you a dime extra, (in fact I am sure that it almost every case I can save you lots of money) and there is absolutely no commitment.