The Diamond 4Cs: Cut

Art. 157

The Diamond 4Cs: Cut
Diamond, with its enchanting sparkle, gives us particular emotions every time we look at it. Most of the secret concealed behind the diamond's appearance is related to its structure and cut quality. Diamond is the hardest natural material and has unique optical properties, but in its rough state, you can't see the dazzling display of light that makes it so desirable. Careful planning, cutting, and polishing are necessary to unlock the optical potential hidden within every rough diamond crystal. So the way a diamond is cut plays a crucial role in determining how alive a diamond will look. For this reason, cut is considered by many diamond professionals the most important of the diamond's 4Cs. But what is precisely the diamond cut? How is it judged? And how it affects the diamond's beauty and value? Let's discover all of these and more.

What is Diamond Cut?
Diamond cut refers to how well- proportioned and finished a diamond is. Proportions of a diamond are the angles and relative measurements of the diamond's tiny flat surfaces called facets and the relationships between them. The finish consists of two qualities: polish and symmetry. Polish is the overall condition of the polished diamond's facet surfaces. Symmetry is the exactness of the diamond's shape and facet arrangement. Proportions and finish together affect the diamond’s overall cut grade and constitute the so-called diamond make. Diamonds with good make will have a dazzling face-up appearance, showing the following three diamond optical properties magnificently: 

  • Brightness (brilliance): the combined effect of the diamond's internal and external white light reflections.
  • Fire: the rainbow colors that result from the dispersion of the white light traveling through the diamond (in practice, the white light entering the diamond is split into the visible spectrum colors).
  • Scintillation: the pattern of light and dark areas and the spots of light, or sparkle, you see when the diamond, the light source, or the observer move. 

It is essential to don't confuse the diamond cut with the shape and cutting style. The shape refers to the outline of the stone, like round, oval, pear, heart, octagonal, or marquise. Different shapes can combine with different cutting styles, the most important of which are the brilliant cut, step cut, and mixed cut. The brilliant cut has many triangular and kite-shaped facets arranged to deliver maximum brilliance and fire. Step cuts usually consist of long and narrow rectangular-, square-, or tapered-shaped facets that create a less sparkling and more sober look. Mixed cut, instead, combines brilliant-cut and step-cut styles. 

Diamond Cut Scale
The Gemological Institute of America (GIA) developed a precise cut grading system that applies to the standard round brilliant cut diamonds - the most used in diamond jewelry - in all clarities across the D-to-Z color range. A standard round brilliant diamond's cut is evaluated on a scale composed of five cut grades: Excellent (Ex), Very Good (VG), Good (G), Fair (F), and Poor (P). 
Diamonds with Excellent-to-Very Good cut grades will reflect and return light to the viewer in the best way, so they will look alive, sparkling, and brighter than poorly-cut diamonds, which instead are lifeless, dull, and often with prominent dark areas, even if they have the same size, color, and clarity. 

Evaluating Diamond Cut
Diamond cut grade is the most complex to determine among the diamond's 4Cs. The GIA cut-grading system considers several factors in assessing the cut grade of a standard round brilliant diamond. These include:

  1. Face-up appearance factors of brightness, fire, and scintillation, which diamond graders evaluate under controlled lighting conditions.
  2. Design factors, which include diamond proportions, durability, and weight relative to its diameter. Diamonds weighing more or less than their face-up appearance suggests will receive a lower cut grade. At the same time, features that make the diamond more vulnerable to damage during setting or wear (e.g., a diamond with extremely thin girdles) also receive a negative cut grade.  
  3. Craftmanship factors that are related to the finishing details. This category involves a rating for polish and symmetry, observing the stone under 10X magnification. A symmetrical and well-polished diamond has an even and superior display of brilliance, fire, and scintillation. When graders evaluate the symmetry of a diamond, they look at things like the evenness of the stone's outline and the symmetry and size of its facets. Instead, the polish evaluation considers the presence of blemishes (i.e., external clarity characteristics) and their overall visibility at 10X magnification. Diamond graders describe symmetry and polish as excellent, very good, good, fair, or poor.

Diamond Proportions and Cut Grade
Diamond proportions play the most crucial role in determining the diamond's cut grade because they significantly affect the performance of the light that strikes the diamond's facets. To better understand the interaction between the light and a finished diamond is essential to know the basic proportion components of a polished diamond: from top to bottom, the main parts of a standard round brilliant cut diamond are the crown, the girdle, and the pavilion. Some polished diamonds also have a tiny flat facet at the bottom of the pavilion, called culet. The large, flat facet on the top, instead, is the table.

Every angle and facet of the diamond affects the amount of light reflected by it and returned to the viewer's eye. Suppose the light enters through the crown of a poorly-proportioned diamond. In that case, light leakage from the pavilion might make the diamond look dark and unattractive. A well-proportioned diamond instead will reflect more light through the crown. In general, an extremely large table, a very steep o very shallow crown, a very deep o very shallow pavilion, or an extremely thick or very thin girdle negatively affect the diamond's face-up appearance and the cut grade. In any case, the way a diamond look face-up arises from the combined effect of the different diamond proportions and not from one single proportion value. So no single set of proportions defines a well-cut diamond, and various combinations are possible to make a diamond beautiful.

Beyond the Cut Grade
Even though the cut grade expresses how well a diamond is cut, it is essential to underline the GIA diamond cut grades represent a range. Diamonds with the same cut grade might look different when viewed face-up. So it would help if you always went beyond the cut grade and the proportion values you read on a diamond grading report by looking at the diamond in person. 

Another crucial issue regards the lighting conditions under which you look at diamonds in the jewelry store. In most cases, you will see a lot of glare, so that it will be hard to note the differences between one diamond and another in terms of cutting quality. You should look at the diamond in the following three different lighting environments and choose the diamonds that is best for you: 

  1. Diffused lighting, i.e., any type of light that does not come from a single point but is scattered together, such as that produced by day-light equivalent fluorescent lamps. This light suppresses fire and enhances the diamond's brightness and scintillation when the diamond is moved.
  2. Spotlighting, i.e., point-source lighting such as direct sunlight, is best to see the fire.
  3. A combination of diffused lighting and spotlighting creates a more balance between brightness, fire, and scintillation. 

Diamond Cut and Value: final notes
The quality of diamond cut has become increasingly important in the jewelry market. As with the other 4Cs of the diamond, the higher the cut grade, the more expensive the diamond is because diamonds with good proportions, symmetry, and polish are dazzling and with every facet displaying the craftsman’s skill and care. Thanks to the superior brilliance, fire, and scintillation of a well-cut diamond, it is possible to lower the color and clarity grades and obtain an even so beautiful diamond but at a lower per-carat prize. In any case, what is always important is that the diamond you are buying is most attractive for your eyes.

October 12 2021