For centuries, diamonds were thought to possess mystical powers due to their resistance and luster. The idea of defacing them by cutting or shaping was unheard of, for it was thought they would lose their powers. They were kept in natural form and held as talisman or lucky charms by religious and political leaders prior to being set as jewels.

It was in the 11th century that diamonds were first worn as ornamentation. In 1074, a Hungarian queen set her crown with unpolished, uncut diamonds. While very beautiful, the stones are not nearly as brilliant as those of today. Surprisingly, this trend did not catch on until the 1300’s when French and English royalty began flaunting diamond jewelry.

The Scaif

In the 14th  century, it became known that the appearance of a diamond could be enhanced by grinding and polishing the rough stone to unleash the beauty of the diamond. It was shortly after this that a man from Antwerp, Lodewyk van Berken, invented the scaif. 

This revolutionary machine contained a disk lubricated with olive oil and imbedded with diamond dust.  The rough diamond was held by a “dop” against the disk, as the diamond dust ground the stone creating flat reflective facets and producing a more brilliant gem.

This new innovation encouraged many cutters to flock to Antwerp to study this new method and soon after, the diamond-cutters guild was established in the same area.

The Diamond Saw

While the popularity and demand for cut diamonds increased, there were no key innovations in the diamond cutting industry until the twentieth century.

With the invention of the Diamond Saw, it was now possible to cut against the grain of a diamond without destroying it.  It also allowed cutters to correct sub-par cuts or irregularly shaped stones. 

This process had its drawbacks.  It was more costly than cleaving, to saw a carat of diamonds, it required 1/10th carat of diamond dust and it took a considerably longer amount of time to cut through a diamond than cleaving (it took days to saw through a 2 carat stone).  Nonetheless, it became the preferred method for cutting diamonds.

Tolkowsky Contribution

Maybe the biggest advancement in diamond cutting to this day came from a young man by the name of Marcel Tolkowsky. In 1919, at age 21 he published a 104 page book called Diamond Design.  In this, he managed to prove on paper what many cutters were attempting for years through trial and error.  In Diamond Design, he explained his formula for maximizing the refracted light while minimizing the amount of sacrificed light.  In short, maximizing brilliance, and inventing the beginnings of the Modern Round Brilliant Cut Diamond.

Now that cutting diamonds could be described in a mathematical format, semi-automatic machines could be developed to do the job of the polishers, and that is just what DeBeers did in the 1960’s.  These machines still required trained workers to oversee the process, but they could be trained to operate these machines in months rather than years.

Sources:
http://www.edwardjayepstein.com/diamond/chap11.htm
http://www.missioncollege.org/depts/math/clouse/wendi.htm