Diamond Cut

The traditional 58 facets in a round brilliant diamond, each precisely cut and defined, are as small as two millimeters in diameter. But without this precision, a diamond wouldn’t be nearly as beautiful. The allure of a particular diamond depends more on cut than anything else. Though extremely difficult to analyze or quantify, the cut of any diamond has three attributes: brilliance, fire (the dispersion of light into the colors of the spectrum), and scintillation (the flashes of light, or sparkle, when a diamond is moved A diamond cut is a style or design guide used when shaping a diamond for polishing such as the brilliant Cut does not refer to shape (oval,princes,pear), but the symmetry, proportioning and polish of a diamond. The cut of a diamond greatly impacts a diamond’s brilliance, this means if it is cut poorly, it will be less luminous. In order to best utilize a diamond material proprieties, a number of different diamond cuts have been developed. A diamond cut constitutes a more or less symmetrical arrangement of facets, which together modify the shape and appearance of a diamond. Diamond cutters must consider several factors, such as the shape and size of the crystal, when choosing a cut. The practical history of diamond cuts can be traced back to the middle ages, while their theoretical basis was not developed until the turn of the 20th century. Design creation and innovation continue to the present day: new technology notably laser cutting has enabled the development of cuts whose complexity, optical performance, and waste reduction were hitherto unthinkable.

Cut Definitions

A diamond’s cut is an integral factor in determining its brilliance and fire. Even a flawless diamond will appear dull and muted if the cut is poor. When evaluating the cut of a diamond, there are some core characteristics that should be considered:

Depth & Depth Percentage

A diamond’s depth can be determined by measuring the entire stone’s height from the table to the culet and is described in millimeters. The depth percentage measures the ratio of the stone’s depth (from the table to the culet) to the diamond’s total diameter. To learn about the ideal depth percentage for each diamond shape, visit our Diamond Shape page.

Table & Table Percentage

A diamond’s table is the largest facet of the stone, comprising the flat surface on the top. The table percentage is the ratio of the width of the diamond’s top facet in relation to the width of the entire stone. The right ratio results in a large amount of fire and brilliance. To learn about the ideal table percentage for each diamond shape, visit our Diamond Shape page.

Measurements

Measured in millimeters, the measurements of a diamond’s length, width, and height are used to evaluate the symmetry and quality of its cut.

Proportions

A diamond’s proportions, a measure of the number and size of facets and its overall length and width, are integral in determining the quality of its cut. When a diamond is cut with the ideal proportions for its shape, it will reflect more light out of the top, resulting in higher levels of fire and brilliance. A poorly cut diamond with incongruous proportions will allow light to escape out the bottom and sides, resulting in a dull, dark appearance.

Crown

A diamond’s crown extends from the top of the stone (the ‘table’) down to the girdle (the widest point of the diamond). Crowns can be comprised of step cut facets or brilliant cut facets.

Girdle

This is the portion of the diamond between the crown and the pavilion, essentially spanning the width of the stone from side to side. The measurement of the girdle represents the perimeter of the diamond. A diamond’s girdle can be rough, polished, or faceted, and does not typically affect the quality or appearance of the stone.

Pavilion

Located at the bottom of the diamond, the pavilion is integral to the stone’s light reflecting properties. A properly cut pavilion will allow the maximum amount of light to reflect from the surface of the stone. An excessively deep or shallow diamond can cause light to escape out the bottom and sides, reducing its sparkle.

Culet

The smallest facet of a diamond, the culet is located at the very bottom of the stone. If the diamond ends in a point, the diamond grading report will show a value of ‘None’ for the culet designation. This small facet was originally intended to protect the diamond’s pavilion, although today’s settings are usually strong enough to render it unnecessary.

Facet/Faceting (Step-cut/brilliant-cut)

With modern diamond-cutting techniques, there are two common methods of cutting facets, each with its own unique light reflection properties:

Step-cut faceting

In this approach, the facets are elongated and placed in rows to simulate a mirrored staircase.

Brilliant-cut faceting

This technique creates triangular-shaped facets that face outwards from the center of the diamond.

Polish, Symmetry, Cut Grade

A diamond’s polish and symmetry are critical to the quality of its cut. For maximum brilliance, every facet of a diamond should be professionally polished after the cutting process. A high-quality polish will leave little to no scratches and marks, while a poor polish can result in imperfections on the surface of the diamond, which detract from its value.

A symmetrical diamond will have well-balanced, properly aligned facets, resulting in a high level of fire and brilliance. If the facets are not symmetrical or not optimally shaped, they’ll display less sparkle.

A gemologist assigns a cut grade as a means of measuring a diamond’s proportions, craftsmanship, quality of polish, and light reflecting properties. A diamond with a high quality cut grade will exude a large amount of brilliance and fire.

A diamond’s ratings for symmetry, polish, and cut grade may vary based on which Gemological Laboratory is evaluating it, as each agency uses a different scale. View our Certification page for more details.
Diamond

Cut & Value

The quality of a diamond’s cut has a significant impact on its value. A well-cut stone sacrifices more of the rough diamond during the cutting process, resulting in a higher market value. It will also exhibit better light reflecting properties, exuding greater fire and brilliance. Improperly cut diamonds will have less visual appeal and a decreased value. To ensure the best value, look for a certified diamond with polish and symmetry ratings of ‘Good’ or better.

Cut & Depth

It’s the cut of a diamond that determines how much light is reflected back to the wearer, directly impacting its brilliance and fire. Diamonds are generally categorized into three main types of cuts:

Shallow cut

Although a shallow cut diamond will create the illusion of a larger stone, it allows light to escape out the sides instead of reflecting off the top, creating a lack of brilliance and sparkle.

Ideal cut

If you’re seeking a high quality diamond that beautifully reflects light, this is the cut for you. This premier cut style is well-proportioned and carefully angled to achieve a luminous appearance.

Deep cut

This type of cut poorly reflects light, resulting in a dull, muted appearance.
Diamond

Light’s Effect on a Diamond

There are many factors that determine a diamond’s brilliance, the most important of which is its ability to reflect light. As a diamond is moved through a light source, tiny flashes will be visible within the stone. Commonly known as sparkle, this is also referred to as scintillation, an effect of the stone’s reflection and refraction of light.

1. Reflection

When light enters the surface of a diamond, a portion of it is reflected back out of the top.

2. Refraction

The remaining rays of light travel into the center of the diamond and bounce off its internal walls, an effect known as refraction.

3. Dispersion

As light exits the diamond, dispersion causes the white light to be separated into multiple colors. Some light will escape out the bottom and sides, and some will reflect out of the top of the stone. The light that is reflected is referred to as the ‘fire’ of the diamond.