Marcel Tolkowsky

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Marcel Tolkowsky (1899-1991) was a member of a Belgian family of diamond cutters and an engineer by education. He is generally acknowledged as the father of the modern round brilliant diamond cut. Developed by Marcel Tolkowsky in 1919, the American Standard (also known as the American Ideal Cut, Tolkowsky cut, and Tolkowsky Brilliant) is the benchmark in North America. It was derived from mathematical calculations that considered both brilliance and fire of diamonds. Later modifications of round brilliants differ in minor ways.

The design was published in 1919 by Tolkowsky in his book Diamond Design.

[edit] Limitation of Tolkowsky Proportions

It has been indicated that Tolkowsky's "ideal" model has been overused contemporarily.^{[citation needed]} The original model was intended to be a set of general guidelines; several aspects of a diamond's cut had not been accounted for or explored. Following are excerpts from a GIA article, "What did Marcel Tolkowsky really say?"[1]:

"Because every facet has the potential to change a light ray's plane of travel, every facet must be considered in any complete calculation of light paths. Just as a two-dimensional slice of a diamond provides incomplete information about the three-dimensional nature of light behavior inside a diamond, this two-dimensional slice also provides incomplete information about light behavior outside the diamond. A diamond's panorama is three-dimensional. Although diamonds are highly symmetrical, light can enter a diamond from many directions and many angles. This factor further highlights the need to reevaluate Tolkowsky's results, and to recalculate the effects of a diamond's proportions on its appearance aspects.

"Another important point to consider is that Tolkowsky did not follow the path of a ray that was reflected more than twice in the diamond. However, we now know that a diamond's appearance is composed of many light paths that reflect considerably more than two times within that diamond. Once again, we can see that Tolkowsky's predictions are helpful in explaining optimal diamond performance, but they are incomplete by today's technological standards."