Diamond Cut: The Most Important C

Sharif Khan
Sharif Khan
Last Updated    EST 
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The cut is often considered the most crucial aspect of purchasing a diamond. It pertains to the brilliance of a diamond and governs how light interacts with it. However, it should not be confused with a diamond's shape, which pertains to its overall outward appearance. The diamond's cut exerts its influence on the stone's appearance through three fundamental avenues:

  • Brilliance: This measures the brightness resulting from a combination of reflected and refracted light.
  • Fire: It characterizes how a diamond scatters light, manifesting as vibrant bursts of discernible colors.
  • Scintillation: This term encapsulates the captivating sparkle that a diamond emits when set in motion.

A well-executed cut allows light to travel through the stone, reflecting from side to side. The light then bounces off the stone, becoming visible to the eye. In diamond terminology, this phenomenon is known as "brilliance."

Creating jewelry through diamond cutting is a delicate and esteemed craft. It encompasses both science and art—science in adhering to precise angles based on proportions and art in crafting a final shape that radiates exquisite beauty.

Be sure to check these True Heart and A Above Diamonds for their Brilliance.

Cut's Importance

The diamond cut is perhaps the most critical factor in assessing brilliance, fire, and scintillation. Given that it is the only C that is not a natural but a human factor, it can be manipulated to save much of the original rough diamond while cutting it. 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 be finalized for fancy-shaped diamonds, such as the cushion or Asscher cut. The cut range is from Ideal/Excellent to Very Good, Good, Fair, and Poor.

Understanding the GIA's cut grading system:

  • Excellent grade: This category has high scintillation, brilliance, and an even pattern of dark and light areas.
  • Very good: Despite high scintillation and brilliance, diamonds in this grade are darker in the edges or center. Notably, a diamond can sometimes have a higher scintillation and brilliance, but its pattern will lower the grade
  • Good grade: This category is slightly dark and has lower scintillation. A diamond's weight ratio or pattern can be downgraded.
  • Fair grade: A gem in this grade has slight scintillation and brilliance.
  • Poor grade: Gems in this grade have inferior proportions and display slight scintillation or brilliance.

True Heart Diamonds

Since non-round-shaped 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 it is cut—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. Pay particular attention to depth percentage of a diamond because 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.

Key Cut Realted Terms

Diameter – The width of a diamond as measured through its girdle.

Table – The largest facet of a diamond usually occurs at the top of the stone.

Culet – The facet at the bottom tip of a diamond. The ideal culet is never visible to the naked eye and is often graded as Small or None.

Depth – The height of a diamond from its culet to the table.

Girdle – The narrow band around the widest part of a diamond.

Pavilion – The bottom part of a diamond, from the girdle to the culet.

Crown – The top part of a diamond, from the girdle to the table.

Cut Grading System

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

After the diamond is reduced to a reasonable size, the cutter uses bruting or cutting to give it its shape. When diamonds are cut by hand, it is called "bruting," while cutting is done using 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 it can be lost. Lastly, because many qualities of a diamond depend upon its cut, the cutter's skill is vital.

The GIA Cut Grading System for brilliant round diamonds is defined and allocates one of five cut grades: poor, fair, good, very good, and excellent. It is based on predictive metrics and the observation and computer modeling of diamonds' appearance. With the help of a prognostic computer model, the system estimates the beauty and brilliance of diamonds based on interrelated specifications. The GIA cut grading evaluates seven elements: scintillation, brightness, and fire based on appearance, while the other four rely on craftsmanship and design, such as weight ratio, polish, durability, and symmetry.

Diamonds must be cut to get a shape, but the term "cut" actually refers to their proportions. The depth and width at which a diamond is cut determine its characteristics, regulating brilliance and radiance. There are two main types of cuts: brilliant cuts and fancy cuts. Brilliant cuts are the most popular and saleable, while fancy cuts include modified brilliants, step cuts, mixed cuts, and rose cuts. Rose cuts are often found in antique jewelry and are making a comeback due to their vintage appeal.

The quality of the cut affects the amount of light and how it exits the diamond. If the cut is too shallow compared to its width, the light will exit directly with little reflection, making the diamond appear dull. Conversely, if the cut is too deep, the light will escape from the sides, also reducing its brilliance. The rarest and highest quality cut is the signature ideal cut, which maximizes brilliance by reflecting light throughout the entire diamond. A cut's quality can be categorized as signature ideal, ideal, very good, good, fair, or poor.

Diamonds are cut into various shapes, and the natural shape and qualities of the diamond determine which cut is chosen for the best effect. When custom designing or shopping for diamond jewelry, it is essential to understand the terminology used to describe different cuts.

The diamond cut is a crucial aspect in determining the value of a diamond and can account for up to one-third or more of its appraisal. This is because certain cuts waste more of the raw diamond in the cutting process, making diamonds that waste more costlier. Besides shaping, different cuts also affect how light passes through the diamond, influencing its brilliance and sparkle.

Cut Attributes

Below are key elements that make up a cut and how it affects a gem's appearance.

Diamond Cut


It refers to the quality of diamond facets due to the polishing procedure or the blemishes left after the cutting procedure. Polish elements are situated on the surface and do not visibly penetrate the gem when viewed at 10x magnification. It is evaluated on a scale comprising excellent, very good, good, fair, and poor. Most diamonds have imperfections since craftsmanship mistakes leave polish marks. Hence, their facets must be carefully polished at the end of the cutting procedure to minimize errors.

Perfectly-polished diamonds must have excellent smoothness and exceptional regularity to ensure they do 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. Thus, 14 dead spots in equally set-apart three-D areas can cause the facet to be non-polishable. The dead regions are often situated on the cube and octahedron faces. For fire and brilliance to not be affected, cutters must ensure that the facets do not coincide with the dead spots. Artisans can move the facets, which make up the symmetry, so that they can shine.


Diamond symmetry is the alignment and appropriate positioning of its facets. A professional artisan will set each facet proportions that complement the surrounding facets. The placement must be completed professionally since the facet junction that does not align will make the stone look uneven. Moreover, the symmetrical quantity of a perfectly cut diamond will deter excessive carat weight in the profile. This makes the gem look heavier than it is.

Additionally, the alignment of facets will define the stone's interaction with light. Some light that hits the stone immediately reflects as a surface stare. A portion of the light that gets into the stone escapes via the bottom and does not visually impact the viewer. A very shallow or deep cut will let light leak from the diamond's internal wall or crown, making many facets dull or dark. As a result, the general appearance will be less sparkly and brilliant. Conversely, appropriately placed facets can maximize the amount of light reflecting from refracts or tabletops and bouncing off the internal walls into an observer's eyes.

The visual impacts of the external and internal interactions with graying 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 shows in the gem, it causes fire

as it is dispersed into a rainbow of shadows-like colors. If the light source, the diamond, or the viewer moves, the spots of light that spackle (flash) will be noticeable.


The girdle in the GIA cut grading system refers to the narrow unit separating the pavilion from the crown and works as the stone's setting edge. It reduces 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 percentage using the available formulae. Therefore, the maximum and minimum verbal descriptions depend on the decisions 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 non-contact optical measuring gadget. With the GIA multipurpose gemological reticule and microscope, you can also measure it. Girdle thickness evaluation depends on visual observations because the measured outcome results are vulnerable to the variability inherent in measurement gadgets. This also holds when differentiating between very thin and exceptionally thin girdles.

Diamond culet size

A diamond culet is a tiny spot where the latter and the facets meet beneath the pavilion. The pavilion facets are uniformly crafted in many stones at the right angle and close at the perfect point, leaving 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 to the stone's cumulative number of facets.

  • 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 of approved diamonds, with culets ranging from small to extremely large.

Here is a description of the culet size:

  • Note: Since there is no space beneath the pavilion, light cannot escape 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 that leaks light under magnification. However, the diamond will have incredible sparkle 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 serves as a window that drives light and defines the brightness of the stone. It also acts as a prism that disperses light, giving the crown facet size, fire, and angel. This will help you define the amount of fire the diamond releases. The crown facet also curvatures light such that what you observe via the crown is a shifted version of what you can see via the table.

A crown angle is created where the girdle plane meets the bezel facets—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 with crown angles are more shallow than 25 degrees tend to be bright but 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, surrounding the gem with a rim of precious metals. Shallow stones are ideal in jewelry where they are not susceptible to damage. The craftsman who cuts diamonds from rough attempts to achieve the largest girdle diameter and high weight retention. Therefore, they are usually cut with shallow pavilions and crowns and have a large table percentage and thin girdles.

  • Ideal Crown Angels

The crown angle compensates for the bending light caused 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 a crown angle that maximizes the proper return for any designated pavilion angel.

Experts calculated that the perfect crown angle is 34.5 degrees paired with a 40.75-degree pavilion angle. Remember that for stone with a 40.7 pavilion angle that curves light too much, you require a crown angle of 35 degrees to 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 are mirrors, and their reflective index defines a stone's ability to work as a mirror. The reflective index represents 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 a perfect angle greater than its acute angle.

A pavilion angle is vital in determining whether a diamond is proportioned correctly or if the stone will require re-cutting. In addition, the table reflection technique helps identify the pavilion depth/angle when it comes to mounting. In most cases, a space in the mounting under the culet allows a direct measurement of the entire depth.

If the general depth of a pavilion is greater than 63 percent with a shallow crown, it is considered deep. For instance, visually, you can identify a flat crown by looking at the stone's side profile and a normal or medium girdle.

  • Ideal Pavilion Angles

40.75 degrees is the ideal pavilion angle, according to mathematics professionals. Interestingly, artisans cut the stones at this angle before it was defined. Diamond cutters claim that beyond 41 degrees, it is 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. Hence, what takes place is not a cliff but a smooth transition from stronger to weaker light as more rays escape.

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

Painting and Digging Out

Printing and digging out refer 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 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. Note that painting and digging out methods on cut grading are affected by the virtual distinguishability of the techniques and if the pavilion or crown or both utilize them.

Proportions for Each Shape

Popular Diamond Shapes

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.

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

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

Cushion Cut Diamonds: A unique diamond shape makes 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, making a statement in a solitaire engagement ring setting.

EMERALD Cut Diamond: The emerald cut diamond 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 high-quality diamond to preserve its clarity.

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 traditionally chosen for diamond engagement rings; however, its unique blocked corners make it a great choice in a setting that does not hide this feature.

PEAR Cut Diamond: The pear shape is like the marquise but with one end rounded and the other 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.

Radiant Cut Diamonds: These are versatile with square shape and trimmed corners. This cut 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.

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, more modern settings and can be accentuated with baguette-style diamonds or gems.

HEART Cut Diamond: Heart-shaped diamonds are considered the ultimate and romantic of all diamond shapes. Besides its shape, the skills required for a diamond cutter to bring out a diamond's natural brilliance and create the smooth profile of a heart determine its value. The heart diamond cut makes for an excellent engagement ring with its tapered point and rounded lobes.

PILLOW Cut Diamond: The pillow cut combines the round and princess cuts with lots of facets, resulting in sparkle and fire. The cushion cut is one of the most common cuts on antique diamonds and is very popular in pendants and other large settings.

Final Thoughts

While Tolkowsky's ideal diamond cut is considered exceptional, only a few diamonds will achieve the perfect Tolkowsky cut and formation. However, any diamond cut with the right proportions will exhibit similarities in brilliance.

It's important to note that there is an ongoing debate in the diamond industry regarding how diamonds should be cut and the potential for innovation and experimentation. Different experts and stakeholders have varying opinions on what constitutes the best cut for diamonds, and this diversity of perspectives fosters ongoing discussions and exploration in the field of diamond cutting.

diamond cut selection

When buying diamonds online, stick to our recommended proportions for each shape to ensure you get a well-cut stone with optimal brilliance. However, obtaining a diamond with full brilliance also involves considering the physical appearance and other quality characteristics of the stone.

If you are shopping locally, examine diamonds under different light conditions after collecting a shortlist of prospective diamonds. Retialers often use fluorescent lights, which may not showcase the diamond's true appearance. Therefore, view the diamonds under various lighting sources, including fluorescent and incandescent lights and direct sunlight. This will give you a better understanding of the diamond's personality and how each cut influences its fire and brilliance. Comparing your shortlisted diamonds to each other can help you make a more informed decision.

Finnaly, when diamond shopping, trust your instincts and have the final say. Choose the diamond that feels "right" and comfortable to you or immediately grabs your attention when you interact with it. This personal connection with the diamond is essential in ensuring you are satisfied with your purchase.