While nature determines a diamond’s clarity, carat weight and color, an expert cutter is required to unlock the fire with a perfectly proportioned cut. A diamond is cut and polished with an exact number of facets. It’s proportions are derived by mathematical calculation.
The table outline will appear to bow out.
In a well cut diamond, the light strikes each pavilion facet at an angle which allows most of the light to reflect back to the crown (top). As it passes through the crown facets at a low angle, the light refracts upon exit. In this case, refraction is a good thing, as the bent light travels to the observer's eye and is perceived as a lively fire.
If the diamond cut is too shallow, entering light strikes the pavilion facet at a low angle and passes through the facet (refracts), escaping through the bottom of the diamond.
If the diamond cut is too deep, entering light strikes the first pavilion facet at an angle sharp enough to reflect to the second pavilion. But the light strikes the second pavilion at too low an angle, causing the light to refract (pass through the facet), escaping through the bottom of the diamond.
Diamonds can be cut into different shapes. Choosing a diamond shape is a matter of personal preference. All shapes are beautiful if they are cut well, including Marquise, Oval Pear, Radiant, Heart and Emerald. But all fancy shapes have inherent difference in the physics of light.
The most popular shape is the Round Brilliant Cut which commands more of a premium per carat because more of the rough is cut away to form the round shape.
Square Emerald Cut
A Square Emerald or "Asscher" cut is a step cut with angled corners and rows of pavilion and crown facets that run parallel to the girdle. “Asscher” is a term commonly used in the marketplace to describe these square Emerald cuts. The term is derived from the Asscher family name. The Royal Asscher Diamond Company currently produces the “Royal Asscher” cut, which is a patented square step cut with an extra row of facets on top and bottom, a notable high crown, and 74 total facets.
The emerald cut diamond is among the most classic of diamond shapes. Inclusions are more visible in the emerald cut. Because of their design, rectangular cut diamonds require more weight to be directed toward the diamond’s depth to maximize brilliance. Depth percentages of 70% to 78% are not uncommon.
This unique shape harkens after an older cut that has now become popular again. They typically have rounded corners and larger facets which can increase their brilliance. Cushion-cut diamonds are available in shapes ranging from square to rectangular or oval. Some cushions have soft, bowed out sides and others have straight edges. Each cushion outline, shape and brilliance is unique.
An oval diamond has brilliance that is similar to a round diamond. The oval shaped diamonds can accentuate slender, long fingers. The length-to-width ratio is important and will determine the diamond’s outline. Ratios between 1.33 and 1.66 are most traditionally accepted for ovals.
The Marquise Cut is a regal, elongated shape with both ends tapered. When choosing an elongated diamond be careful to avoid the ‘bow-tie’ effect. Also, with a marquis cut the length to width ratio should be considered
Although this shape is most often used in pendants, an elongated pear shape can create a slimming effect on the finger. The preferred length-to-width ration is between 1.45 and 1.75
This shape is the perfect choice if you prefer a square or rectangular outline but want the brilliance of a round. Because of their design, square cut diamonds require more weight to be directed toward the diamonds depth to maximize brilliance. Depth percentages of 70% to 78% are not uncommon.
The radiant cut is a beautiful combination of the classic emerald cut and the sparkle of the round brilliant. Because of their design, rectangular cut diamonds require more weight to be directed toward the diamond’s depth to maximize brilliance. Depth percentage of 70% to 78% are not uncommon.
Diamonds cut into this shape possess a high crown, small table, and a large, flat culet. With 58 facets, it is the predecessor of today’s modern round brilliant cut. The Old European cut dates to the 1800s and was used mostly during the Victorian, Edwardian and Art Nouveaux eras.
The rose cut features a flat bottom with a dome-shaped crown, rising to a single apex. With anywhere from 3 to 24 facets, a rose cut diamond resembles the shape of a rose bud. The rose cut dates to the 1500s and remained common during the Georgian and Victorian eras.