What is Diamond Cut?
Diamond Cut refers to how well proportioned the diamond is. For example, what percentage of a diamonds diameter is its depth? What are its various angles and how do they interact with one another? While these may seem like esoteric questions, these are the essential factors that determine how beautiful your diamond will be. For a great visual representation of why these issues matter, have a look at James Allen’s page on Diamond Cut.
Diamond Cut Grade — All that Matters
Until January 1st, 2006, you basically had two options when it came to diamond cut grade. You could either buy a diamond with an AGS certificate and trust their diamond cut grading system, or you could learn about the various proportions of diamond cut and trust your own education about what numbers translated into a beautiful diamond. On that day, though, the GIA introduced a new certificate format that included their very own diamond cut grade. They claim that their Diamond Cut Grade system is based on 15 years of research testing and retesting different combinations of measurements with real life light performance tests. As opposed to the AGS system which simply defined what an “ideal” diamond is and then gives lower grades the farther away from that “ideal” the parameters are (see table to the left), the GIA system does not have any one single definition of perfection. They claim that in their research various differing combinations of proportions equally produced diamonds that reflected the most light. So while in the AGS model, a diamond with a table size of 60% is automatically penalized to a Diamond Cut Grade of “2,” (on a scale from 0 to 9), with the GIA model, there’s still a chance the diamond could receive an “Excellent” grade if the rest of the parameters are the best possible parameters that combine with a 60% table.
In my opinion, the GIA system is clearly a much more elegant solution to the question of what cut proportions produce the most beautiful diamonds. And the fact is, it’s a more elegant solution than your typical diamond dealer’s instincts, as well. What I mean is, before GIA introduced their cut grade, most diamond dealers thought about cut grade the same way the AGS did. They had in their mind what was the perfect set of parameters, and basically, diamonds got uglier the further they strayed from that ideal. This revelation of how GIA Diamond Cut Grade worked was a boon to diamond manufacturers as well. Now, the cutters had more options when assessing a piece of rough for cutting. If a diamond with a 57% sized table couldn’t fit into a certain piece of rough and still maintain the weight category, then they could try a diamond with a 60% table and see if that would maintain the weight.
For those of you looking to buy a diamond without a certificate, here’s a very dumbed-down, but reliable rule of thumb. Just remember “60/60.” That means 60% table and 60% total depth. While this falls out of the “0″ and “1″ cut grade of the AGS, it is the basic rule of thumb that diamond dealers always use. You can allow for about 2% plus or minus from the 60%, and make sure the girdle size is either thin or medium, but not thick. With these simple rules, you can be assured you will end up with a very beautiful diamond.
Ira Weissman recommends you to visit http://www.truthaboutdiamonds.com for more information on diamond cut.