The cut is often acknowledged as the most important aspect when buying a diamond, and hence should not be confused with the shape. It refers to the brilliance of the diamond. Simply put, the way a diamond is cut will determine how light is reflected through the stone.

A good cut will allow the light to travel through the stone and reflect from side to side. The light then reflects out of the stone, which is what you see with your eye. In diamond terminology, this sparkle is “brilliance.”

Cutting diamonds to become jewelry is a delicate and highly regarded craft. It is both science and art—science in that certain angles must be precisely followed based on proportions and art in that the final shape must exude a high-class beauty. A diamond cut should not be confused with its shape, which refers to the general outward appearance.

The Cut of a Diamond is Important:

Diamond cut is perhaps the most critical factor in assessing the overall brilliance and fire of a diamond. Because it is the only C that is not a natural element but a human factor, it can be manipulated to save rough parts while cutting a diamond. The Gemological Institute of America (GIA) has developed a comprehensive system for assigning cut grades to round brilliant cut diamonds. However, it has yet to finalize it for fancy-shaped diamonds, such as a cushion or Asscher cut.

The cut range is from Ideal/Excellent to Very Good, Good, Fair, and Poor. Since non-round shape diamonds do not have a cut grade in a GIA report, we recommend that you follow our guidelines for each diamond to determine how well a diamond is cut; for example, follow this guide for an oval cut diamond. The most important factors to consider while assessing a diamond’s cut include the depth, table, girdle, crown angle, pavilion angle, and culet. You should especially pay attention to depth as it can be substantial at times, making a 1-carat diamond look like a 0.7ct. Please follow our diamond proportions guidelines for precise information on each shape.

How GIA Cut Grade System Works.

The GIA Cut Grading System for brilliant round diamonds is defined and allocated one of five cut grades: poor, fair, good, very good, and excellent. The GIA system is based on predictive metrics, observation of the diamonds’ appearance, and computer modeling of diamond appearance. With the help of a prognostic computer model, the GIA system estimates the beauty and brilliance of diamonds based on interrelated specifications.

The GIA cut grading is based on the evaluation of seven elements. Three elements—scintillation, brightness, and fire—are based on appearance, while the other four on craftsmanship and design, including weight ratio, polish, durability, and symmetry.

Here is an outline that will help you understand the GIA’s cut grading system and what differentiates an excellent from a good or fair cut.

● Excellent grade: This category has high scintillation, brilliance, and an even pattern of dark and light areas.

● Very good: While this grade has high scintillation and brilliance, they are darker in the edges or the center. Sometimes, a diamond can have a higher scintillation and brilliance, though its pattern will lower the grade.

● Good grade: This category is slightly dark and has lower scintillation. Weight ratio or pattern can downgrade a diamond.

● Fair grade: A gem in this grade has slight scintillation and brilliance.

● Poor grade: Gems in this grade have inferior proportions and display little scintillation or brilliance.

Understanding the attributes of diamond appearance:

Here are some of the elements that make up a cut and how it affects the gem’s appearance.

Polish

Polish is the quality level of diamond facets due to the polishing procedure or the blemishes made after the cutting procedure. Polish elements are situated on the surface and do not visibly penetrate the gem when viewed at 10x magnification. Polish is evaluated on a scale comprising excellent, very good, good, fair, and poor. Most diamonds have imperfection since craftsmanship mistakes bring polish marks. To lessen the mistakes, each diamond facet must be carefully polished at the end of the cutting procedure.

Perfectly-polished diamonds must have excellent smoothness and exceptional regularity such that it does not have burn marks, nicks, wheel/polishing marks, lizard skin, or abrasions. Nevertheless, the surface of the diamond is anisotropic, implying that there are harder and softer zones. For this reason, there are 14 dead spots at equally set-apart three-D areas that can cause the facet to be unpolishable. In most cases, the dead regions are situated at the cube and octahedral faces. For the fire and brilliance to not be affected, cutters must ensure that the facets do not coincide with the dead spots. Craftsmen can move the facets, which will comprise the symmetry, to ensure that all the facets are polished.

Symmetry

Diamond symmetry is the alignment and appropriate positioning of its facets. A professional craftsman will put each facet in proper proportions that complement surrounding facets. The facet placement must be completed with professional precision since the facet junction that does not align will make the stone look uneven. Moreover, the symmetric quantity of a perfectly cut diamond will deter excessive carat weight in the profile. This makes the gem look right for its actual weight.

Additionally, the alignment of facets will define the interaction of the stone with light. Some light that hit the stone immediately reflects as a surface stare. A portion of the light that gets into the stone escapes via the bottom—this light will not have any visual impact on the viewer. A very shallow or deep cut will let light escape through the diamond’s internal wall or crown, making many facets appear dull or dark. As a result, the general appearance will be less sparkly and brilliant. Appropriately placed facets can maximize the amount of light reflected from refracts or tabletops and bounces off the internal walls to an observer’s eyes.

The visual impacts of the external and internal interactions with greying light establish the brilliance of a diamond. Scintillation will be caused by an equal balance of light and dark spots, creating a clear pattern with no distracting dark outline. Once the light exists in the gem, fire is caused as the light is dispersed into the rainbow of shadowlike colors. In case the source of light, diamond, or the viewer moves, the spots of light that spackle (flash) will be noticeable.

Girdle

The girdle in the GIA cut grading system refers to the narrow unit that separates the pavilion from the crown and works as the stone’s setting edge. It plays a role in lessening the risk of damage when adequately thick, comprising 16 hill and 16 valley positions formed by the final cutting. An optical gadget calculates the average thickness and its percentage computed using the available formulae. Therefore, the maximum and minimum verbal descriptions depend on the decision of GIA lab graders.

The thickness is evaluated as a range from the thinnest to the thickest valley spots. The maximum and minimum girdle thickness is measured via the use of the non-contact optical measuring gadget. You can also measure it with the GIA multipurpose Gemological Reticule and a gemological microscope. Girdle thickness evaluation depends on visual observations because the measured outcome results are vulnerable to variability intrinsic in measurement gadgets. This holds true when differentiating between very thin and exceptionally thin girdles.

Diamond culet size:

A diamond culet is a tiny spot beneath the pavilion where the latter and facet meet. In many stones, the pavilion facets are uniformly crafted at the right angle and close at the perfect point, making no culet. If the pavilion facet does not meet at an ideal point, the culet will be a rough or polished facet. The existence of the culet adds an extra facet to the stone’s cumulative number of facets.

● Rating of culet size

A diamond culet can be rated from extremely large to none. When loose diamonds are sent for certification, the stone is observed face up to determine the culet’s size and sideways to define its angle. A sharply angled culet is not evaluated as a culet but as an additional facet. Diamond culet size is expressed as a percentage relative to the diameter for approved diamonds with culets ranging from small to extremely large.

Here is a description of culet size:

● None: Since there is no space beneath the pavilion, light cannot space from the culet and is bounced back. It is a requirement for well-cut grade diamonds.

● Very small: The culet comprises a tiny opening that is invisible without magnification. Since light seepage is reduced, it cannot affect the gem’s light performance and sparkle.

● Small: This culet has a noticeable opening under magnification that leaks some light. However, the diamond will have great spackle and high brilliance.

● Medium: A visible opening is noticeable under magnification, though tiny without it. This will affect the light performance of the stone since light leaks via the pavilion’s center.

● Large: The culet is visibly open and serves as a facet. Leakage of light takes place, affecting the brilliance of the stone.

● Very large: A vast opening is available in the stone. You cannot see the brilliance of the stone’s cut.

Crown angle:

A crown angle refers to the angle created where the girdle plane meets the bezel facets—it is the same as the crown height. Therefore, a higher crown means a greater angle. Most diamonds have crown angels that range from 25 to 35 degrees. Diamonds whose crown angles are shallow than 25 degrees tend to be bright, but they are more vulnerable to damage than gems with high crowns.

Diamonds with shallower crowns must be placed on mountings to secure the girdle spot, such as bezel settings, that surround the gem with a rim of precious metals. Shallow stones are ideal to be used in jewelry where they are not susceptible to damage. Diamonds cut from rough are a task for the craftsman who attempts to achieve the largest girdle diameter and high weight retention. For this reason, they are usually cut with shallow pavilions and crowns. Additionally, they have a large table percentage and thin girdles.

● Ideal crown angels

The crown angle tries to compensate for the bending light by the initial pavilion. In this case, the general concept is that the crown angle must be shallow if the pavilion angle is steeper to compensate for light and vice versa. This implies that there is a crown angle that maximizes the right return for any designated pavilion angel.

Experts calculated that the perfect crown angle is 34.5 degrees paired with 40.75 degrees of pavilion angle. Bear in mind that for stone with a 40.7 pavilion angle that curves light too much, you require a crown angle of 35 degrees so that you can compensate. Similarly, if a stone with a pavilion angle of 41 degrees does not bend light correctly, you will need a shallower crown angle of 43 degrees to compensate.

The pavilion angle:

The lower girdle facet and pavilion serve as mirrors, and its reflective index defines a stone’s ability to work as a mirror. The reflective index defines the viewpoint that light is curved at while it gets into the diamond. The angle is vital since stone can only serve as a mirror when the light hits at a perfect angle greater than its acute angle.

A pavilion angle plays a vital role in determining whether a diamond is proportioned correctly or if the stone will require re-cutting. The Table reflection technique is useful in identifying the pavilion depth/angle when it comes to mounting. In most cases, there is a space in the mounting under the culet that allows a direct measurement of the entire depth.

You will know that a pavilion is deep if the general depth is more than 63 percent with a shallow crown. For instance, visually, you identify a flat crown by looking at the stone’s side profile and a normal, medium girdle.

● Ideal pavilion angles

40.75 degrees is the ideal pavilion angle, according to the mathematics professionals. Interestingly, artisans were cutting the stones with this angle before it was defined. Diamond cutters claim that beyond 41 degrees are too steep. Retailers selling badly cut stones will lure you by saying that a cliff of 41 degrees is ridiculous. However, according to physics, there is a critical angle before light escapes. What takes place is not a cliff but a smooth transition from stronger to weaker light return as more rays escape.

The aspect you need to remember is that transition happens around 41 degrees. Therefore, unless you observe a super-ideal gem cut at 40.9 degrees, you are good to choose something close to 40.75 degrees. While using a light ray tracing, researchers have found that a pavilion angle that is shallow than 40.5 degrees is exceptionally shallow and will result in light leakage and obstruction.

Painting and Digging Out:

Printing and digging out refers to the faceting methods for the half facet that influence the stone’s three-dimensional settings. They include the relative position, horizontal angles, and distance from the center of the stone. The painting and printing out methods are applied to save the stone’s weight during the cutting procedure. They get rid of attachments near the girdle or influence the face-up appearance of the gem. You must note that painting and digging out methods on cut grading are affected by the virtual distinguishability of the techniques and if utilized by the pavilion only, crown only, or both.

 

 

More about Diamond Cuts:

Diamonds must be cut to get a shape; the diamond’s actual cut refers instead to its proportions. The depth and width at which a diamond is cut determine its characteristics. The cut of the diamond regulates brilliance and radiance. Diamonds are typically cut in brilliant cuts and fancy cuts. Brilliant cuts are perhaps the most popular and are often the most saleable. Fancy cuts include modified brilliants, step cuts, mixed cuts, and rose cuts. Diamonds with rose cuts are generally only seen in antique jewelry. Rose cushion cut jewelry is steadily making a comeback as an antique appeal is becoming more popular today.

The amount of light and the way it exits a diamond depends on the type of cut and is often referred to as the quality of the cut. If the cut is too shallow than the cut’s width, for instance, the light will directly exit the diamond with little to no reflective qualities, making it appear dull and lusterless. Likewise, if the diamond cut is too deep, the light will escape from the diamond’s sides rather than through it, leaving the stone dull. A Signature ideal cut is perhaps the rarest and highest quality cut available. With this cut, the light that enters the diamond is reflected in such a way that it encompasses the entire diamond and allows for maximum brilliance and radiance. A cut’s quality can be Signature ideal, ideal, very good, good, fair, or poor.

Diamonds are cut from stones in a wide variety of shapes known as cuts. While most stones can be cut into any of these shapes, the diamond’s natural shape and qualities will determine which shape is chosen for the best effect. Suppose you are custom designing your diamond jewelry or shopping for an already designed piece. In this case, it is always helpful to understand the terminology used to describe the different cuts used for diamonds. The name of the cut refers to the shape of the diamond when viewed from above.

The diamond cut is one of the most critical aspects in attributing value to a diamond and can sometimes account for up to one-third or more of a diamond’s appraisal. It is generally so because certain cuts waste more of the raw diamond in the cutting process—diamonds that waste more cost more.

In addition to the shape, different cuts will differently affect how light passes through a diamond. In this way, how a diamond is cut will also determine its brilliance and sparkle.

MOST POPULAR DIAMOND CUTS:

1. ROUND Cut Diamond: One of the most common shapes for a diamond used on rings, pendants, bracelets, or earrings is the round shape. The diamond sides are faceted to allow the light to reflect across the diamond center, creating the fire and sparkle that is the hallmark of beautiful stone. Round diamond cuts are trendy for solitaire style rings and are ideal for stud-type earrings.

2. PRINCESS Cut Diamond: Another widespread diamond cut for the large or center stone or in a solitaire style setting is the princess cut. This cut is the square to rectangular cut seen in many of the antique and modern settings. Diamonds used for the princess cut have to be superior in clarity to prevent the color from showing at the cut’s points or corners.

3. Cushion Cut Diamonds: A unique diamond shape made for an exciting alternative to the princess or oval cut diamonds. It has rounded corners and larger facets that help bring out its brilliance. The cushion diamond is a beautiful combination of round and square and makes a statement in a solitaire engagement ring setting.

4. EMERALD Cut Diamond: The emerald cut is a rounded rectangle with a pavilion or faceted side, typical of what you would see in a well-cut emerald gem. Like the princess cut, the emerald shape requires a very clear diamond of high quality to preserve the clarity.

5. ASSCHER Cut Diamond: A less common cut is the Asscher, a square version of the emerald cut. The difference between the Asscher and emerald cuts is that the former (Asscher) is square rather than rectangular. This cut is not a traditionally chosen cut for diamond engagement rings; however, its unique blocked corners make it a great choice in a setting that does not hide this feature.

6. MARQUIS Cut Diamond: The marquise cut is an elongated shape with both the top and bottom ending in a noticeable point. This shape is ideal for enhancing the size of the solitaire diamond as it draws the eye along the cut of the side, giving the appearance of a much larger carat diamond. The marquise cut is seen in older and more modern settings and can be accentuated with baguette-style diamonds or gems.

7. PEAR Cut Diamond: The pear shape is like the marquise but with one end rounded and one end pointed. This diamond cut can add a slimming and elongating effect to the ring finger and is considered one of the classic diamond shapes. Pear-shaped diamonds are also famous in earrings and necklaces, where they give the impression of length.

8. Radiant Cut Diamonds: With its square shape and trimmed corners, the radiant cut diamond is versatile, given that it combines the classic emerald shape with the brilliance that nearly matches a round cut diamond. It is quite similar to the princess cut but is usually slightly more in the shape of a rectangle, having its corners blocked.

9. Pillow Cut Diamond: The Pillow cut is a combination of the round and princess cut with lots of facets resulting in sparkle and fire. The cushion cut is one of the most common cuts seen on antique diamonds and is very popular in pendants and other large settings.

10. Oval Cut Diamonds: As the name says, the oval cut diamond is oval and the most near to that of the round cut diamond. This cut features a flattering, more extended outline that combines with the brilliance of a round cut diamond. Additionally, oval cut diamonds are popular engagement ring choices because their length can accent longer, slenderer fingers.

CHOOSING THE BEST DIAMOND CUT:

It should be noted that there is no distinct “best” diamond cut available. Take, for example, Tolkowsky’s cut. While this diamond cut can have exclusive parts that make it distinctive from the rest, other diamonds will have some similarities in characteristics. Only a few numbers of diamonds will have the perfect Tolkowsky cut and formation. The “perfect” Tolkowsky cut will only be visible on finely and expertly cut diamond stones.

But some diamond craftsmen are using their licenses in creating similar cut diamonds and selling them at cheaper rates. This kind of problem has been mixed with the fact that there is no final industry agreement on how diamond cuts are named. Another issue when buying diamonds based on cuts is that each will be defined with some personal touch in mind. Famous cuts in different regions reflect these kinds of preferences.

1. Check the grade of how the diamond was cut. To do so, look at the diamond grade certificate to find even better stones cut at even better forms. Only stick with the “Excellent,” “Very Good,” and “AGS” grades.
2. After collecting your prospective diamonds, examine this shortlist by putting them under different light conditions. Grading laboratories and companies use fluorescent lights for grading their stones. This unfavorably affects the diamond’s appearance. Hence, try viewing the diamond under several fluorescent lights, incandescent lights, and direct sunlight.
3. Doing this will surely help in getting the feel of the personality the diamond gives off. Compare your shortlist to others’ so that you can distinguish the impact and effect that each cut has on the stone’s fire and brilliance elements.
4. Always have the final say when diamond buying and make your decision based on what you truly desire. Opt for the diamond that makes you feel “right” and comfortable or the one that grabs your attention when you try to move it.

Generally, the more depth a diamond has, the more brilliance it will have. To calculate a diamond’s depth percentage, divide depth by width and multiply by 100. Before a diamond is cut, the diamond cutter must analyze the diamond. Two factors are important: maximizing the investment return and how fast the diamond can be sold. For maximizing the return on a diamond, the cut is essential. The cutter has to look at several factors, such as weight and color retention, the shape of the rough stone, and the location of inclusions and flaws.

Diamond cutting involves four different methods: cleaving, sawing, bruting/cutting, and polishing. Cleaving is the first step in diamond cutting, which cuts a rough diamond down to a manageable size using wax or cement mold. The cutter cleaves the diamond along its weakest point called the tetrahedral plane. At other times, a diamond cannot be cleaved when there is no point weakness, and the cutter uses either a phosphor-bronze saw blade or a laser. However, lasers take a long time.

After the diamond is a reasonable size, the cutter uses either bruising or cutting to give them their shape. When diamonds are cut by hand, it is called bruting, while cutting uses a lathe. In either process, one diamond is used to cut another. After the diamonds are cut, the cutter uses a rotating polishing wheel coated with an abrasive powder to finish the diamond. When a diamond is cut, 50% of the stone can be lost. Considering so many qualities of a diamond are dependent upon cut, the cutter’s skill is vital.

Conclusion

The cut of the diamond stone should not be your only basis when buying a diamond. There are other important factors to consider, such as how the price will fit your budget. Before deciding what kind of diamond cut to go with, consult SGDX gemologists in diamond cutting and check the polishing.

Credit: Sharif Khan on 23rd Jul 2021