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In The Mind of a Diamond Cutter – Part 2

I want to talk about how important the cut is when selecting a diamond.  As with everything else to do with diamonds, there’s not a 100% clear cut answer.  To make things just a bit more confusing for y’all, every laboratory has their own system.  One lab’s “ideal” is another lab’s “very good”.  How are you supposed to know which to trust?  Read on…

Round Brilliant Cut Diamonds

In 1919,  mathematician Marcel Tolkowsky, wrote a Masters thesis on the proportions for round brilliant cut diamonds. This became the basis for what is now known as the “Ideal Cut”.  Basically, there are specific parameters that a round diamond has to be cut by in order to achieve maximum sparkle (in our last blog we talked about why diamond cutters don’t cut them all to perfection).  When a cutter achieves these specific requirements, the result is a superior cut diamond… and more brilliance, sparkle & fire. 

Most laboratories have used words like “very good” or “ideal” to describe how well their diamonds are cut.  This is with the exception of American Gem Society (AGS).  They have chosen a simple number scale of 0-10.  “0” is the highest cut grade possible and therefore ideal (included in ideal as well are cuts 1 & 2).  10 is the very worst cut… and then there is everything in between. 

How do we know which cut number it should be?  Canadian Jewelry Exchange invests heavily in state of the art equipment to grade diamonds.  This Sarin machine measures every facet of diamond by laser & prints a small report to tell us what the cut grade is. 

Grading a loose diamond at

It’s a far cry from the diamonds when I attended GIA for diamond grading and was handed a ruler about 1/2 an inch long!  And the math… ugh… math is not my strong suit.  But I’m getting off topic :0)

A really well cut round brilliant cut diamond hides many sins.  It can camouflage inclusions, enhance the color and get ready for people grabbing your hand and shrieking “oh my goodness, what a gorgeous diamond!!!”

Fancy Cut Diamonds

Remember, any diamond that is not a Round Brilliant Cut is considered a “fancy cut”.  It is very important to note that cut grade is not determined on any fancy cut by any laboratory.  There is simply no standard (yet) for how well a princess or pear, etc should be cut to maintain maximum sparkle.  That may change- I’ve heard the gossip that both AGS & GIA are working on determining the ideal proportions for a princess cut… but as of yet, this does not exist.  If you are shopping for a diamond and are told this is an “ideal cut princess cut”, it is only in the opinion of the store/salesman as the certificate will not confirm this.  Consider these two GIA certifcates: see how the one for Round Brilliant Cut has a Cut Grade of Excellent?  Note on the GIA certificate for the Square Modified Brilliant (the techie name for Princess), there is no cut grade at all.

GIA certificates from

Again, this may change.  But for now, if you are shopping for a fancy shape, you absolutely must see the diamond with your own eyes to determine if it is aesthetically pleasing to you.  If it is, that’s all that matters.

We have GIA trained staff ready to help you find your perfect diamond & explain all the nuances of cut, clarity, color & carat in as much (or as little) detail as you need.  Come visit & we’ll help you make a great decision.

– Lisa


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