Ideal Cut Diamonds

The pursuit of perfection is a human calling. The diamond -- already perfection in the eyes of most -- has been cut and shaped in an ever-changing variety of ways since modern cutting techniques were invented, all in an effort to maximize its full potential for brilliance.

Predecessors of the modern round brilliant, such as the European or Old Mine cut, were fairly deep stones with very small tables, large culets and short pavilion facets; there was no single standard way of cutting them and diamonds from that time therefore vary widely in appearance. However, in 1919, diamond cutter Marcel Tolkowsky published a doctoral dissertation that would change all of that. Using only his own visual assessments of different variations of diamond cuts, he presented a theory about the cutting angles which would create the most proportionate balance of brilliance and dispersion in a gem-quality diamond. Tolkowsky's measurements for achieving the "Ideal Cut" were exact and strict: a 34½° crown angle with a 53% table, which created a 16.2% crownheight; and 40¾° pavilion angle combined with a 43.1% pavilion depth. Improved cutting techniques and technology which were being developed at the same time finally allowed cutters to achieve these more precise and stream-lined designs.

Despite Tolkowsky's theories, opinion regarding diamond proportions was not unanimous. Tolkowsky's measurements were eagerly adopted and adhered to by the American Gem Society (AGS). However, by the beginning of the 1950s, a backlash had begun and diamond cutters increasingly moved away from the ideal cut and toward diamonds with shallower crown angles -- angles as low as 32½°-- and larger tables of 60% and even 64% or 65%. Many went so far as to argue that the proportions of the Ideal Cut created an inherent over-abundance of dispersion, or "fire," which distracted from the diamond's brilliance. As proof that the Ideal Cut was not an absolute embodiment of perfection, they pointed to Eastern cultures, which actually considered larger tables more beautiful than the smaller ones which typified an Ideal Cut. Even those who embraced the Ideal Cut realized the impracticality of cutting diamonds to such a specific set of parameters and soon modified its definition by expanding the acceptable table size from Tolkowsky's original 53% up to nearly 58%.

Against this backdrop of disagreement, The American Gem Society (AGS) opened its own lab in 1996. They sought to bring the public trust into their camp by providing independent documentation to confirm the superiority of the Ideal Cut. To accomplish this, the AGS began to grade and certify cut and proportions -- something that had previously not been done by other labs. These grades were based on how closely a given diamond's cut conformed to the standards established by the Ideal Cut. The grading scale ranged from 0 (the finest quality) to10 (poor quality). Diamonds that fell within the Ideal Cut range were, of course, graded as 0. AGS's influence on the Ideal Cut's rise in popularity is evidenced by the fact that, today, the term "AGS zero" is synonymous with the Ideal Cut.

By the time the AGS Lab opened its doors, the Ideal Cut was no longer conceived of as only the single set of proportions set forth in Tolkowsky's original dissertation. Rather, it was regarded as a design based on a narrow range of combinations of proportions. " (Source: "The Ideal Cut: A Consumer's Guide")

The range is:

 Table Diameter: 52.4% to 57.5%

 Crown Angle: 33.7 degrees to 35.8 degrees

 Girdle Thickness: Thin to Slightly Thick (.51% to 2.95%)

 Pavilion Angle: 40.2 degrees to 41.25 degrees

 Culet: None (Pointed) to Medium

 Total Depth: 56.88% to 63.92%

How are a Diamond's "Proportions" Measured?

These proportions can only be measured using a precisely-tuned instrument called a Sarin Dia Mension proportion grading machine. The same machine used by AGS. View a Sample Sarin Diamond Grade Report (DGR) which should be included with all diamonds greater than .25ct.

No machine can measure a diamond's quality of finish (this work is done by a highly trained gemologists). The AGS 0 cut grade also means that a diamond possesses ideal symmetry and polish.

However, in recent years the term "ideal cut" has been adopted by many jewelers, especially on the internet, to loosely describe any diamond that falls within these "general" cutting parameters, or has a small table. Beware of claims of "ideal cut" without documentation of the diamond's specific proportions, e.g., crown and pavillion angles. You may end up paying a premium for a diamond that really isn't "ideal cut". Technically, Ideal Cut is a brand name for diamonds that both fall within the Ideal range and are accompanied by an AGS certificate or at a minium a Sarin report.

Recent research suggests that while the Ideal Cut has grown in popularity and draws a premium price, it is really just a matter of personal opinion. Many combinations of cut proportion can produce a brilliant, firery diamond, while at the same time, cutting flaws can drastically detract from a diamond's ability to refract light. Ensure the diamond seller you deal with can discuss the exact diamond proportions with you and has the documention to illustrate all the cut proportions.