New Round Brilliant Diamond Cut Grade

Let's begin with the Ideal Cut:  Given that the diameter of a diamond equals 100% - The table of an Ideal Brilliant cut diamond should be 53-58% and the depth 59.3% plus the girdle thickness. The crown should be 16.2% with a 34 degree angle, and the pavilion should be 43.1% with a 40.75 degree angle.  This proportion formula, originally described by Marcel Tolkowsky in the year 1919, was purported to allow maximum brilliance and dispersion of all light striking a round brilliant cut diamond.

From my perspective of selling diamonds for more than 26 years, the most common downside to a consumer who focuses on finding a diamond with these exacting proportions is that he or she has forgotten the most basic premise of buying a diamond:  beauty and romance.  If you get so completely caught up in the numbers you tend to analyze and worry yourself throughout the whole diamond shopping experience and forget that it all comes down to how brilliant and pleasing the diamond is to the eye and even more importantly that it is a symbol of your unending love and devotion. 

I have witnessed time and again a woman say, “Honey, I love this diamond, this is the one I want”, only to be disappointed since “Honey” is so analytical the he completely missed the simplicity and importance of buying the diamond that she wants.  Instead he exclaims, “This diamond has a 60% table! That won’t do!” ETC…

I have seen hundreds of diamonds over the years that did not fit exactly into the Ideal Cut mold yet were incredibly beautiful, brilliant diamonds.  Apparently so have the Gemologists and Scientists at GIA. 

GIA began a study in 1989 using a computer model to determine how light behaves within a round brilliant cut diamond.  They only recently concluded that 15 year study, at a cost of millions of dollars, involving intensive research of more than 38 million proportion combinations and over 70,000 human observations on 2300 diamonds. 

Essential findings as reported in the Fall 2004 Gems & Gemology include:

• Proportions need to be considered in an interrelated manner.  The combination of proportions is more important than any individual proportion value.
• Attractive diamonds can be manufactured in a wider range of proportions than would be suggested by historical practice or traditional trade perception.
• Personal preference still matters.  Diamonds with different appearances can be found within each cut grade, so individuals need to look at the diamond itself, not just its grade, to choose the one they like the best.

The conclusion of this study provided GIA with the knowledge that there are many different sets of proportions for top grade diamonds and an even wider set of proportions for very pleasing upper grade and middle grade diamonds. 

As a result GIA has developed a new cut grade system that considers the combination of seven components: brightness, fire, scintillation, weight ratio, durability, polish and symmetry.  This new cut grading system includes five grades: EXCELLENT, VERY GOOD, GOOD, FAIR, and POOR.  The new GIA Diamond Grading Reports will include an overall cut grade of the diamond and expanded proportion information.

What does this mean to you?  You should know what you are buying when shopping for a diamond.  The four C’s, Cut, Color, Clarity, and Carat Weight, remain the best way to compare diamonds. The new expanded cut grade system gives you a better understanding of the overall beauty of a given diamond from a grade of Excellent to Poor.  Use this knowledge in combination with the Color, Clarity and size you are interested in to make your decision.  But most importantly – after you have considered all these factors you should simply choose the diamond that you like the most!