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The Ideal Cut - Diamond

The Ideal Cut Diamond

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; they 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 this balance were exact and strict: a 34½° crown angle with a 53% table, which created a 16.2% crown height; 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 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) to 10 (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.

What Exactly Is An 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.


  • 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%

  • These proportions are measured by a precisely-tuned instrument called a Sarin. No machine can measure a diamond's quality of finish (this work is done by highly trained gemologists), but the AGS 0 cut grade also means that a diamond possesses ideal symmetry and polish.

    Because AGS was so successful in promoting their Ideal Cut as the "best" diamond on the market, many jewelers have jumped on the band-wagon to make a profit from its popularity with customers. Technically, Ideal Cut is a brand name for diamonds that both fall within the Ideal range and are accompanied by an AGS certificate. However, in recent years the term "ideal cut" has been adopted by many jewelers, either unwittingly or to intentionally deceive customers, to loosely describe any diamond that falls within these general cutting parameters. Customers should also be aware that many jewelers inaccurately use the term to describe any diamond that has a small table.

    Caution: You should consider it nothing less than outright deception if a GIA-certified diamond with a small table is described by any jeweler or diamond retailer as an "Ideal Cut" if it also possesses any of the following qualities:

  • Polish or Symmetry rated as Good, Fair, or Poor

  • A girdle that is extremely thin, thick, or extremely thick

  • Diamonds with these qualities may be attractive and valuable. However, such diamonds are clearly not Ideal Cuts based on the specifications recognized by AGS. Describing such diamonds as Ideal or even as Very Good is an inaccurate representation of the diamond's quality.

    So Is The Ideal Cut Really The Best? Recent research suggests that the answer is really just a matter of personal opinion.

    Around the globe, the Gemological Institute of America (GIA) -- a major supporter of public gemological and diamond education -- is regarded as the leading expert on anything in the gem world. Their recent study on brilliance in diamonds relied on thousands of graded diamonds from the Institute's collection, as well as on thousands of computer simulations which analyzed the way light travels into, out of, and within a diamond. The surprising conclusion of this study was that, while Ideal Cut diamonds do display a great deal of brilliance, they don't necessarily always display the most brilliance. Rather than finding one single range of proportions that were the most brilliant, the study found a number of differing combinations of proportions that could all bring out high degrees of brilliance in a diamond. In fact, at the end of their report in the Fall 1998 issue of Gems & Gemology, William Boyajian, President of the GIA, concluded that:

    "Although it is not GIA's role to discredit the concept of an 'Ideal" cut, on the basis of our research to date we cannot recommend its use in modern times."

    At Jewelry Depot, Inc. (JD Houston) we pay a great deal of attention to the diamond's finish; "finish" refers to a diamond's polish and symmetry. A quality finish is really a statement of the care and skill that the cutter has put into designing the diamond. An Ideal, Excellent or Very Good finish display a rare demonstration of the height of the cutter's art, but a Good finish also offers proof of a carefully and lovingly cut diamond.