Diamond Culet: Is it Important?

The culet of a diamond is the pointed end where the two opposite pavilions meet. This pointed edge at the bottom of the diamond is designed to prevent light from escaping through the base.

Every diamond has a culet, which is graded by the GIA (Gemological Institute of America) based on the size of its opening. The culet grade ranges from "None" to "Very Large," with "None" being the most common. To achieve an "Excellent" diamond cut grade, the culet must typically be graded as either "None" or "Very Small."

diamond culet

Below are the culet grades as defined by the GIA:

None: No opening under the diamond. Light is fully retained, preserving brilliance.
Very Small: The opening is only visible under magnification. Minimal light escapes, and brilliance is well preserved.
Small: A small opening where slightly more light escapes, but brilliance remains high.
Medium: A noticeable opening that causes some light loss at the center of the pavilion.
Large: A more significant opening, leading to noticeable light loss. Brilliance and light performance are affected.
Very Large: A very large opening where most light escapes. The diamond lacks brilliance and appears dull.

The ideal culet grade for any diamond is "None." If you must compromise, the lowest acceptable grade is "Very Small." Any grade beyond this diminishes the diamond's brilliance and prevents the cut from being graded as "Excellent."

Diamonds with no culet opening (graded "None") are more prone to chipping because of their sharp, pointed edge. To reduce this risk, diamond cutters often leave a "Very Small" hole, which preserves brilliance while minimizing the chance of damage.

The culet is the lowest part of a diamond where the two opposing pavilion angles converge. This meeting point closes off the diamond to prevent light from escaping through the bottom. While the size of the culet may vary among diamonds, it is a feature present in all diamonds.

The GIA recognizes that the culet grade contributes to the overall cut grade of the diamond. As previously mentioned, "None" and "Very Small" are the most desirable grades for achieving an "Excellent" cut.

Due to its small surface area and pointed structure, the culet is highly susceptible to damage. This vulnerability requires careful handling during jewelry setting. To protect the culet, diamonds are often mounted in a way that hides and shields this delicate feature.

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TOPLINE

The culet (pronounced as Kullet or Kyoo-lit) is a polished facet located at the bottom of a gemstone, parallel to the table. The term "culet" originates from the Latin word culus, meaning "bottom." The size of the culet, as determined by the GIA (Gemological Institute of America), is classified using the following scale: None → Very Small → Small → Medium → Slightly Large → Large → Very Large.

If a gemstone has no culet facet, its size is reported as "None." Additionally, if the culet is positioned at more than a slight angle relative to the table facet, it is also reported as "None" because it is no longer considered a culet but an extra facet. To assess the angle, graders also examine the diamond in profile view.

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Diamond Culet Size

The culet size impacts the cut quality of a diamond and plays an important role in the GIA's grading process. A culet graded as "None" or "Small" is ideal because it does not negatively affect the diamond's appearance. Ultimately, the beauty and brilliance of a diamond are what matter most. A large or very large culet can allow light to pass through, reducing the diamond's brilliance and diminishing both its visual appeal and market value.

If a diamond has a large culet, light may pass straight through the crown and facet without producing any sparkle, creating a "dead space" inside the diamond. This dead area significantly impacts the diamond's brilliance and overall aesthetic. For this reason, it is ideal for a diamond to have no culet. However, modern diamond cutters often intentionally create a small culet during the cutting process to minimize the risk of chipping.

The culet is usually not visible to the naked eye unless it is unusually large, which is rare. During the cutting and polishing process, the culet is carefully shaped and polished, much like any other facet. A round brilliant-cut diamond typically features 57 facets, with the culet often considered the 58th facet. While a small culet can be observed using a 10X loupe, it is challenging for an untrained eye to detect or evaluate its size.

In conclusion, avoiding diamonds with a very large culet size is recommended, as they significantly detract from the diamond's brilliance. Opting for diamonds with culets graded "None" to "Medium" is a smart choice, ensuring both beauty and structural integrity.

Different Grades of Diamond Culet

The grading system for diamond culet ranges from None to Very Large. Grading laboratories, using 10x magnification, examine the point where the diamond's pavilions meet to close off the diamond. The presence and size of an opening under the diamond pavilion determine the culet grade. The culet plays a crucial role in the diamond's light leakage, brilliance, light performance, and overall cut grade. The grades are as follows:

None: The diamond's pavilion has no opening under it, preventing any light from escaping through the bottom. This ensures maximum brilliance as most or all of the light is reflected back to the observer. Diamonds with excellent cut grades often have this culet grade.
Very Small: A tiny opening under the pavilion is only visible under 10x magnification. Minimal light escapes through this opening, so the diamond retains most of its brilliance and sparkle. This grade has little to no noticeable impact on the diamond's overall appearance.
Small: A small opening under the pavilion becomes more visible under 10x magnification. Some light escapes through this opening, but the diamond still reflects a significant amount of light, maintaining high levels of brilliance and sparkle.
Medium: The opening under the pavilion is noticeable under magnification. At this grade, more light escapes through the opening at the center of the pavilion, slightly reducing the diamond's brilliance and light performance.
Large: The opening in the culet is clearly noticeable and begins to act like one of the diamond's facets. More light escapes, significantly impacting the diamond's light performance and reducing its brilliance and sparkle. Diamonds with large culets, such as old mine cut diamonds, exhibit this characteristic.
Very Large: The opening in the culet is extremely large and highly noticeable. Most of the light entering the diamond escapes, resulting in poor light performance and minimal brilliance. Diamonds with this culet grade appear dull and lack sparkle. This type of culet is typically found in vintage styles like Old Mine and Old European Cut diamonds. Modern and brilliant-cut diamonds never exhibit this culet grade.

The Effect of Culet on a Diamond

The ideal culet size or grade to maximize a diamond's brilliance is “None.” Brilliant diamonds typically have this culet grade—or at most, “Very Small”—which contributes to the exceptional brilliance we admire. A closed edge at the base of the diamond prevents light from escaping through the underside of the pavilion, ensuring that light is reflected back, enhancing the diamond’s brilliance.

Many diamond cutters, however, prefer to create a very small opening at the culet (under the pavilion) for practical reasons. When the diamond has no opening, the two pavilion facets meet to form a sharp, pointed edge at the base. This pointed edge is prone to damage and chipping, especially if the diamond is not handled carefully. To minimize this risk, cutters often include a very small culet opening, which removes the sharp point while retaining the diamond's brilliance. This minor opening escapes minimal light, preserving the diamond's brilliance and sparkle.

On the other hand, large culets are undesirable. They create a "window" through which light escapes, reducing the diamond’s brilliance. When viewed from the top of the table, a large culet appears as an opening, which detracts from the diamond’s aesthetic appeal. Moreover, a large culet can create a visible dark spot beneath the diamond’s table, further compromising its appearance. This effect impacts the diamond’s light performance and diminishes its overall beauty.

The culet is an essential factor in determining a diamond’s cut grade. A poorly graded culet can significantly affect light performance and visual appeal. If you value a diamond's brilliance, choosing a diamond with either no culet or a very small culet is essential. These grades preserve the diamond’s brilliance and ensure it sparkles to its full potential.