What is meant by "Ideal Cut"?

Great question, you'd think there would be a quick and easy answer. But, no.

The term "ideal" has often been used to describe only the best cut diamonds, but it’s also been confused and abused over the years. After 300 years of experimentation and refinement, experts now agree that there's more than one simple way to describe the cut of a round brilliant diamond.

Although he never used the word "ideal" in his proof of Diamond Design (1919), Marcel Tolkowsky argued that a very tight range of proportions – based on Table Percentage = 53%, Crown Angles = 34.5 degrees, and Pavilion Angles = 40.75 degrees – produces optimal fire and brilliance in a finished gem diamond. Like most basic mathematics and physics, his numbers have withstood the test of time. They still hit the "sweet-spot" of most modern ideal standards.

After teaching 1000’s of gemologists about these “ideal” proportions over many years, the Gemological Institute of America (GIA) did not issue proportion-based cut grades on their diamond reports. However, they did recently introduce a performance-based grading system for cut that defines five levels of cut quality - Excellent, Very Good, Good, Fair, and Poor - with the top two grades being the most prevalent.

For the past decade, the American Gem Society (AGS) has pioneered and strongly endorsed the use of “ideal” in conjunction with a consumer-friendly numeric scale of 0 - 10 (with “0” being Ideal) to quantify multiple factors affecting cutting quality. Their Zero Ideal Cut Grade is based on an overall combination of ideal light performance, ideal proportions, and ideal finish – which includes ideal polish and ideal symmetry. This top grade represents just 3% of round diamonds in the marketplace.

There are diamonds that also exhibit extra “ideals" when viewed in various viewing devices. Some show ideal patterns of optical symmetry when you view diamonds directly under specialized filters and lighting environments. Others generate ideal computer-generated numbers, scales, images and guides that compare one "virtual" diamond with another.

But, diamond reports and viewing devices will only ever tell you so much. In the final analysis, I always recommend looking at any diamond you may consider owning. That’s what all the experts I've ever met do.

Why? Because, diamonds are dynamic 3-D works of art! They express their beauty in motion. Their true nature and appeal is impossible to reveal with a mere snapshot. It should not come as a big surprise to find that they often look very different in reality than they do “on paper”.