The Essentials You Need To Know When Purchasing and Caring For Your Diamond.
Diamond Cut

Diamond Proportions

Every diamond has three or four parts: the top (table and crown), the middle (the girdle, the widest area), and the bottom (the pavilion) plus the culet (the base). The size and relationship of these parts to one another are known as the proportions of the diamond, and are very important to the overall brilliance, fire and sparkle of the diamond.

Tolkowsky and the Modern Round Brilliant

Ideal Cut ProportionsIn 1919, Marcel Tolkowsky, a Belgian mathematician, developed a model of faceting and proportions that he determined would result in the most attractive and balanced cut for a round diamond. He published his findings in a paper titled "Diamond Design". His work paved the way for what has become known as the Modern Round Brilliant.

In his model, Tolkowsky traced the path of light two-dimensionally within a diamond and came up with a set of optimal dimensions that would become known as the "IDEAL CUT". Diamonds cut more shallow or deeper were assumed to leak light and be less than ideal. What constituted a beautiful cut diamond was highly contested for the next 90 years in the diamond community and, unlike color and clarity, there was not a widely adopted grading system for cut. This was largely because diamond cutters recognized that there were proportions outside of Tolkowsky's model that also produced brilliant and beautiful diamonds.

About Diamond Cut

Breakthroughs in Understanding Diamond Proportions

Diamond Ray TracingThe Gemological Institute of America (GIA) and the American Gem Society Lab (AGSL) both invested years of research to have a better insight into how light actually travels within a diamond. The Tolkowsky model only took into account two dimensions because that was all that was possible until the late 90's. At that point, new technologies allowed the surface of a diamond to be scanned and the size and location of every facet mapped with great precision. Scientists at the GIA and the AGSL were then able to harness today's computer power to crunch sophisticated three dimensional models using a method called ray tracing. Ray tracing takes a virtual ray of light, passes it through a computerized scan of the diamond and calculates the resulting light output.

Modern ray tracing verified what diamond cutters knew already. There were indeed a range of proportions that, when combined properly, would produce diamonds with high degrees of brilliance, fire and sparkle. By using ray tracing, labs are now able to evaluate the light performance of round brilliant diamonds and they have been incorporating this information into new cut grading systems since January 2006. Round brilliant diamonds now have standardized cut grades provided via GIA and AGSL, just as they have standardized color and clarity grades.