Diamond Cut

Cutting does not refer to the shape of a diamond (for example, round, oval, pear, etc.), but to its proportions, symmetry and polishing. The beauty of a diamond depends more on cutting than on any other factor. Although this is very difficult to analyze and quantify, the diamond cut has three main effects: brightness (brightness created by combining all white light reflections from the surface and inside the polished diamond), glow (scattering of light into the colors of the visible spectrum, considered as color flashes) and scintillation (a flash of light or glitter when the diamond or light source is moving).

When a diamond is made of coarse stone, the cutter must balance the optimal cut (and therefore appearance) from the maximum yield (grape stone virginates, while retaining as much carat weight as possible). Since many customers are willing to pay more for a larger, better-worked diamond than just for a smaller, well-worked diamond, the cutter has to work hard to maintain the weight of the diamond without damaging the appearance. That's why the cut class is so important; This allows the buyer to identify stones of dubious quality that have been processed only to save weight in carats.


From the rough stone on the left (shown in blue), you can get one of the two diamonds:

In-depth processing of diamond (orange) gives a much larger diamond, bringing the cutters a greater profit from its investments.

The total price at which you can sell less, a well-crafted diamond (white) may be lower than a larger diamond, but its price per carat will be higher, not only because of its beautiful appearance, but also because of the reduced yield from rough stone (which makes the creation of a diamond more expensive).


The proportion of the diamond is the ratio between the size, shape and angle of each face of the diamond. A wide range of combinations is possible, which determine the interaction of the diamond with light.

When light hits the diamond, about 20% immediately reflects off the surface (like gloss). With 80% of what remains, a part will go down the bottom of the diamond and will be felt. In order to maximize the amount of light reflected from the crown (top) of the diamond in the eye of the observer, each face of the proportionally processed diamond will have the correct position and angle of inclination. Due to this, the light that is reflected, is perceived as flashes, glow and brilliance.

The table below shows three common modes of light. When light hits any face of a diamond, it will either be reflected (reflected back) or refracted (distorted, passing through the face). The cut of a diamond is very important because the angle at which light penetrates the face determines the process of reflection or refraction of light.

If the diamond cut is very shallow, light will penetrate into the face of the pavilion at a small angle and pass through the face (break), finding an outlet through the lower part of the diamond.
With a deepened diamond cut, the light hits the first pavilion of the face at an angle sharp enough to be reflected on the second pavilion. But the light enters the second pavilion at a very low angle, requiring light to break (go through the face) and find an outlet through the bottom of the diamond.
In a well-crafted diamond, light hits each side of the pavilion at an angle, allowing most of the light to be displayed back to the crown (upward). When light passes through the faces at a low angle, it is refracted at the time of exit. In this case, the reflection of light has a positive character, since the distorted light falls back into the observer's eye and is perceived as a living glow.


The depth depends on the distance between the Kaletta and the flat grandsundian, if you look at it from the side. The depth of the diamond is expressed in millimeters, and is indicated as the third number of the "size" of each diamond (the first two digits indicate the length and width).

The depth of the diamond in percent, is calculated by dividing the depth by the width of the diamond. Thus, if the depth of the diamond is 3 mm, and the width is 4.5 mm, its depth in percent will be 66.7. The smaller the depth in percent, the larger the diameter of the diamond with the given weight in carats (since the greater part of the diamond is the width and depth).


The percentage of the flat face of the diamond is calculated by dividing the width of the flat face of the diamond by the width of the diamond. Thus, if the width of the flat face of the diamond is 3 mm, and the width of the diamond is 4.5 mm, its planar face in percent will be 66.7.


You should not choose or refuse a diamond based solely on its percentage depth or flat face. Since both factors already belong to the common class of Cut, they should be used as the main parameter when choosing a diamond. When comparing two diamonds of the same class, the cut, the percentage depth and the size of the flat face in percent, then can be used for further refinement, especially (in the case of a depth of%) if someone wants to know how big the diamond will look.


The proportions table shows the size of the diamond belt, the size of the culet, the percentages of the depth and the flat face, as well as other dimensions, such as the corners of the crown and the pavilion. The angle and index are measured electronically using a light scanner. The proportions table is a "copy" of your diamond.


Evaluate the combined effects of the shape of the faces and angles, the width of the belt, the size of the culetts, polishing and symmetry of the general diamond depicted is a difficult task even for professional gemologists. Fortunately, all these factors have already been taken into account when calculating the class of diamond cut.

Since the Class of Cutie provides a single rating that weighs the combined effect of all these factors on the appearance of the diamond, this is a simple but important assessment tool.

When evaluating a diamond, the Cutting class should be the first point. Only when comparing two diamonds with the same class of Cut, the individual components of the Cut should be used (for example, belt width, symmetry, polishing, percentage depth, planar face in percentage and callette size) as indicators of additional processing.


Unlike the other "C" (carat weight, color, and purity) to date, there are various classes that are not related to the GIA, and are not used in most situations. In fact, the GIA began to designate classes from 2005, and only for round diamonds.

Although retailers use generic terms to describe Cut (such as Excellent, Very Good, Fair, Weak), there is no clear definition or application of these terms. In fact, the diamond seller can assign any cut class, such as he chooses, based on arbitrary factors. One retailer will use terms such as "Ideal characteristics", "Ideal" and "Excellent"; and the other uses "Perfect" to describe all three, and the other - "Excellent" for everyone. Be careful when comparing the cutting classes of different sources, since they are most likely incompatible.

In addition, one should remember about the diamond sellers who designate their own cut classes, in return, GIA for certain forms of diamonds has already been appointed. Many popular websites and retail stores have their own, more generous evaluation of сut, instead of GIA classification.

The cut class is assigned to the GIA using the following scale:

Excellent Maximum glow and brightness. Reflects almost all the rays penetrating the diamond, creating an exceptional sparkle and vividness of perception.
Very Good Correctly displayed most of the light falling in the diamond, creating a beautiful glow and brilliance. Under normal lighting conditions, it looks very much like an excellent cut, but at a lower price.
Good Reflects most of the light falling on the diamond, with an average similarity degree of the appearance of the diamond, indicated above. Excellent value compared to the level of cut.
Satisfactory Allows most of the light to penetrate the diamond, followed by a flight through the sides or bottom, reducing the glow and shine, are perceived. More suitable for diamonds, weighing less than 0.75 carats, where the differences in brilliance are perceived more difficult.
Weak Allows most of the light to penetrate the diamond, followed by a flight through the sides or bottom. The diamond may look imperceptible and dull, even for the naked eye.

Advice to the buyer:

The cut class is the most important factor in determining the general form of the diamond, because a poorly worked diamond will be unattractive, even with excellent purity and color. Conversely, a well-worked diamond can have no lower color level (G-H) or purity (SI1-SI2) and still look good, thanks to its remarkable ability to create brightness and shine. For a wonderful shine, choose a diamond class "Very good" or "excellent" - for a round diamond, and "Good" or better - for diamonds of various shapes. When choosing diamonds in this range, make sure that its symmetry and polishing are very good or excellent. For those who do not want to spend money on a large size, a diamond of the class is Satisfactory - it can be an acceptable choice, especially in attractive shapes and with a good degree of faceting. Despite the lack of scintillation and brightness in a well-processed diamond, this will significantly increase the size for the same price.

Do not buy cut diamonds, even if the size is the most important for you. Most often these diamonds are not sold, despite the lower price.