The Modern Brilliant was born in 1919 from the mathematical calculations of Marcel Tolkowsky. As a member of a family of Belgian diamond cutters he had a certain interest in making beautiful diamonds. As an engineer, he studied the way light behaves within a diamond and determined the combinations of angles, facet sizes and shapes needed to maximize both the fire and brilliance that a diamond displays.
Fire is the term applied to the spectral colors reflected out of the heart of a diamond. Brilliance is the amount of light returned to the viewer. Sparkle, or scintillation, refers to the combination of these two factors.
He determined that if a diamond is cut too deep or too shallow, light will leak out and the diamond will not be as bright or fiery as it could be. Moreover, the shape and size of each facet is important to the amount of light returned to the viewer.
The Modern Brilliant cut consists of 58 facets, or 57 if the culet is excluded: 33 facets on the crown and 25 (or 24) on the pavilion. Contemporary diamonds are usually cut without a culet.
Tolkowsky's model is the basis of every new round brilliant cut. Over the years, advances in science have allowed us to refine these guidelines into spectacularly sparkly diamonds. Some, like the Hearts and Arrows cut, rely on exacting specifications regarding pavilion and crown angles, table size, girdle thickness, facet sizes, and alignment. Alignment refers to how well the crown and pavilion line up. Perfect alignment is when, at the girdle, the points of the kite and crown facets match up with the pavilion mains and lower girdle facets.
You can see in this next image that the precise cutting is somewhat visible in the finished stone without the special viewer. The red viewer images show that the cut is not exactly perfect, as the hearts are not uniform and the arrows are a little off.
This fancy vivid yellow is a stunning example of excellent cutting by Eight Star, the company that pioneered the Hearts and Arrows cut.
Next time, we see how a round brilliant diamond is made.