Tolkowsky’s Cut Diamond
In 1919, Marcel Tolkowsky, a member of a Belgian family of diamond cutters, published Diamond Design, the first recorded analysis of diamond proportions for the round brilliant cut diamond. His work was based on modern theories of light behavior and his opinion of what proportions resulted in what many industry professionals considered to be the best possible balance of brilliance and dispersion of light.
Tolkowsky’s calculations indicate that for optimum brilliance a round brilliant cut diamond should be cut to the following angles and proportions:
- 34 ½° Crown Angle.
- 40 ¾° Pavilion Angles.
- 59.3% Total Depth (excluding girdle thickness) with 16.2% of the depth being comprised of the crown (top half of the diamond) and 43.1% representing the pavilion lower half of the diamond.
- 53% Table based on diamond’s overall diameter.
Tolkowsky’s design is frequently referred to as the “American Ideal Cut” because diamond cutters in the United States began cutting it first… Marcel Tolkowsky’s early model of brilliance sets the stage for the modern AGS-000 Ideal Cut Diamond and Hearts & Arrows Ideal Cut Diamond which are the most brilliant and dispersive diamonds available on the open market today.
Some laboratories like the European Gemological Laboratories (EGL) will say that a diamond is “Tolkowsky Cut” or within “Tolkowsky Range” if the diamond’s proportions are “within tolerance” of Tolkowsky’s original calculations. According to the EGL the specifications for their “Tolkowsky Range” are as follows:
- 33 – 36° Crown Angle.
- 40 – 41.5° Pavilion Angles.
- 56 – 60.5% Total Depth (excluding girdle thickness) with 14 – 16.5% of the depth being comprised of the crown (top half of the diamond) and 42 – 44% representing the pavilion lower half of the diamond.
- 53 – 57% Table based on diamond’s overall diameter.
“Ideal Cut” vs. “Ideal Range”
To the average consumer, the terms “Ideal Cut” and “Ideal Range” might seem like the same thing, however they are actually quite different. Understanding how these terms are used and misused by the diamond industry will assist you in the selection process of your diamond and possibly prevent misunderstandings.
A true “Ideal Cut Diamond” is a round brilliant cut diamond that has been cut to AGS-0 Ideal Cut Proportions as defined in the following table:
- Table Diameter: 52.4 – 57.5%
- Crown Angle: 33.7 – 35.8 Degrees
- Pavilion Depth: 42.2 – 43.8%
- Girdle Thickness: Thin, Medium, Slightly Thick
- Culet Size: None, Pointed, Very Small, Small, or Medium
“Ideal Range” refers to round brilliant cut diamonds that have been cut within a range of variables, similar to, but not as exacting, as Marcel Tolkowsky’s original calculations and outside the parameters of EGL’s “Tolkowsky Range” mentioned above.
Many “industry professionals” would agree that the following proportions are within the “Ideal Range” for a round brilliant cut diamond:
- 31.7 – 37.3° Crown Angle.
- Pavilion Depth of 41.2 – 44.8%.
- 52.4 – 63.5% Table based on diamond’s overall diameter.