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Diamond Education: Cut
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.
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.
A diamond’s table is the largest facet of the stone, comprising the flat surface on the top. The table percentage is the ratio is 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.
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.
Measured in millimeters, the measurements of a diamond's length, width, and height are used to evaluate the symmetry and quality of its cut.
Round diamonds have long been the most popular, although many modern consumers prefer alternative shapes, including emerald, princess, radiant, and asscher, among others.
This is the largest facet of the stone. It comprises the flat surface on the top, resembling a ‘table’.
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.
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.
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.
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.
With modern diamond-cutting techniques, there are two common methods of cutting facets, each with its own unique light reflection properties:
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 centre of the diamond.
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.
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.
Cut & 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.
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.
This is the cut of a high quality diamond that beautifully reflects light. This premier cut style is well-proportioned and carefully angled to achieve a luminous appearance.
This type of cut poorly reflects light, resulting in a dull, muted appearance.