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Diamond ProportionsDiamond 4 C'sChard 24 Carat Home Page

Diamonds Index
Ideal Proportions
Ideal Proportions

Too Deep
Too Deep

Too Shallow
Too Shallow

Diamond Proportions
Modern Brilliant Cut

The first, and probably most important aspect of the proportion of any polished diamond is its depth relative to its diameter. It is also the easiest to measure.

Marcel Tolkowsky made calculations about light travelling through diamonds, using ray tracing. His work is considered limited today, and there had been studies of diamond proportion before his time, certainly from 1751, and well-proportioned diamonds were already being produced by Henry Morse and Charles Field. Tolkowsky was however the first to apply scientific principles and publish the results. These were in a book called "Diamond Design, A Study of the Reflection and Refraction of Light in a Diamond", published in 1919.
Tolkowsky studies were only two-dimensional, and ignored incident light from many different directions, and made a number of other simplifying assumptions. Others have followed and improved on his work since, but his basic conclusions and recommendations were approximately correct.

Simplified Scheme
The three simplified diagrams shown demonstrate what happens to light rays hitting diamonds which are well-proportioned, too deep, and too shallow, in turn. Each diagram shows two perpendicular rays, one entering through the table, the other entering through a kite or bezel facet. These diagrams ignore other important aspects such as the relative heights of the crown and pavilion to each other, and we intend to add further pages dealing with these proportions later. For now, let's consider:-

Facet Names & Names of Other Parts of Polished Diamonds
Names and explains terms such as crown, pavilion, table, kite facet.

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