DIAMOND CUTTING STYLES

Diamond is a mineral made of essentially pure carbon.  It is the only gem made of a single element.  This pure carbon crystallizes in an isometric or cubic structure.  Most diamonds in the rough are in the form of an octahedral crystal.  You could picture this as two four sided pyramids stuck together at their base.  Diamonds are typically cut in an effort to maintain as much of the original rough diamond weight as possible.  A prime example of this is the Old Mine Cut.

OLD MINE CUT

This cut was originally developed in the early 1800’s and probably used well into the 1870’s.  These diamonds were cut solely by hand in the beginning.  Steam power enabled diamond sawing and sped up the cutting process around the 1840’s, however most of the cutting was still done by hand – and the public still preferred the Old Mine Cuts.  The Old Mine Cut diamonds most notably possess a cushion shape as a result of maximizing the octahedral outline, and retaining weight.  Along with the squarish outline this cut typically had a very small table, open or large culet, and often very clumsy symmetry.  These extreme variations in angles and proportions resulted in diamonds ranging from very brilliant to very blocky light return, and fishy, watery and sometimes dead appearances.  It could be said that this gave each diamond a unique personality and distinct beauty just as the bygone era in which they were fashioned, compared to the cuts of today.     

EUROPEAN CUT

Sometime around 1875 the steam-powered lathe, invented by Charles Field, considerably sped up the cutting process and made it much easier to cut a round girdle outline.  About this time the European Cut had emerged and continued into the 1920’s.  Older European cuts were still quite lumpy, probably due to a transition in cutting style from the Old Mine.  There are diamonds out there that are clearly transitional cuts exhibiting influences from both cutting styles.  The European cut typically had a table sometimes as small as 45% up to 57%, a high crown, a large culet, and a thin girdle.  It is common to see chipping around the girdles of these older stones.  The biggest visual difference between the Old Mine and the European is the change to a round outline and a much more symmetrically balanced cut, which improved toward the end of the this cutting style.   

TRANSITION CUT

Also known as the Early American Cut and the Early Modern Cut, this style had a lower crown, more medium table, shorter pavilion and smaller culet. Girdles were not faceted yet. The most significant diamond cutter ot the time was Henry Morse, perhaps the first person to consistently cut diamonds into shapes that were different from the prevailing European cuts. Morse and his partner Charles Field cut diamonds with smaller tables, shallower crown angles, and smaller culets than the European cut. Rathere than cut diamonds only to retain weight, Morse and his cutters attempted to cut every diamond to consistent proportions.  Morse most likely found through practice what Tolkowsky would attempt to determine mathematically.  This cutting style is seen rom around 1918 through the mid to late 1920's.  

MODERN CUT

In 1919, Marcel Tolkowsky described in a book entitled "Diamond Design" a specific mathematical computation of angles and proportions that would allow maximum brilliance and dispersion of all light striking a diamond.  His formula includes the following:  Given the diamond’s diameter to be equal to 100, the table should be 53%, total depth 60 to 61%, crown depth 16.2%, and pavilion depth 43.1%.  Also ideal crown angle should be 34.5° and optimum pavillion angle 40.75°.
This new cutting style was becoming increasingly popular in his time, especially in America. Different versions of this style would become known as the Tolkowsky Cut, the Modern Brilliant Cut, and the American Ideal Cut.  Although Tolkowsky wasn't the first to suggest diamond proportions in these ranges, he was the first to publish a mathematical foundation that supported them.  These proportions might not have been too different from those that had been used by Morse and others in America.  Along with the Transition Cut, Tolkowsky’s cutting style led to different appearances than those of Old European and Old Mine cuts that were prevalent at the time.

Unfortunately these proportions proved to be quite expensive to produce.  This led to more spread stones with tables sometimes reaching 65% and larger as most cutters would cut a diamond to retain maximum carat weight regardless of the proportions, while still attempting to produce a brilliant diamond.  For many years very few cutters were cutting the recommended 53% - 57%  table.  The majority of cutters were cutting table sizes larger than 60%.  Plus the majority of the buying public seemed to prefer the 60% tables as this gives the appearance that the diamond is actually larger even though the beauty is somewhat diminished.

In the past twenty years the public seems to have become more educated.  More and more consumers are expecting a diamond certificate with their significant diamond purchases, and more often are interested in better proportions.  Diamonds are being cut today more frequently within what’s become the Ideal Cut range.  It is rare to find a diamond that meets Tolkowsky's original standards, however the Ideal range for a round brilliant diamond typically would include a depth of 59% to 61% and a table of 53% to no more than 59%. These proportions theoretically will handle most of the light that enters the surface of the diamond's crown and return it with maximum brilliance and dispersion to the observer's eye! 

But Wait!  The Gemological Institute of America recently concluded a study that encompassed 15 years of intensive research of more than 38 million proportion combinations and over 70,000 human observations on 2300 diamonds to prove that there were many proportion combinations other than Tolkowsky’s that potentially provided maximum brilliance and dispersion.  My next guide will cover these exciting new findings.