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Diamond Cut

Along with clarity, colour and carat weight, cut is one of the four Cs, used to determine a diamond’s value. When talking about a diamond’s cut do not confuse the term with a description of the stone’s shape. While shape describes the outline of the stone when viewed from above – for example, round, oval, or square - cut refers to a diamond’s proportions and its ability to disperse and reflect light. The way a diamond is cut determines its brilliance and so is often considered to be one of the most important characteristics.

The proportions of the diamond are measured precisely to encourage the light to bounce about and refract inside the stone, increasing its brilliance. A stone that is cut too shallow looses light through the bottom; one that is cut too deep looses light from the sides and may appear darker. A stone cut to the ideal proportions allows the light in, and then reflects it back up through the crown of the stone to the viewer’s eye.

Hatton Jewels Diamonds

Diamond Anatomy

When thinking about buying a diamond it is helpful if you understand as much as you can about all the characteristics of the precious stone.

When a diamond is well-cut, light enters through the table and travels to the pavilion where it reflects from one side to the other before reflecting back out of the diamond through the table. This light creates a diamond's beautiful brilliance.

The image below shows the attributes of a diamond, some of which are used to measure a diamond's value.

In the table below, there is a breakdown of the anatomy of a cut diamond to explain more about how a cut grading is calculated.

 The width of the diamond, which is measured through the girdle.
 The large flat facet that makes the upper most face of the diamond.
 The upper portion of the diamond from the girdle to the table.
 The bottom portion of a diamond, extending from the girdle to the culet.
 The outer edge of the diamond, between the crown and pavilion.
 The tiny facet at the tip of a gemstone – often not visible to the eye.
The measurement from the culet to the table. 

Cut Grading

The higher the cut grade the more expensive the stone will be. Cut gradings are listed in the table below.

A rare and beautiful cut, reflects nearly all light that enters the diamond. This however can only be applied to round diamonds.
 Very Good
 Reflects almost as much light as the excellent cut.
 Reflects most light that enters.
 A good quality diamond, but less brilliant than a good cut.
These diamonds are generally deep and narrow or shallow and wide and reflect the light poorly.

Symmetry and Polish

Pay particular attention to the symmetry of the cut and its final polish, both have a significant effect on the diamond’s brightness and overall quality.

Poor symmetry can cause light to be misdirected as it enters and leaves the diamond, and can affect the diamond's brilliance.

Symmetry is rated as:

  • Excellent (EX)
  • Very good (VG)
  • Good (G)
  • Fair (F)
  • Poor (P)

Polish grade describes the smoothness of the diamond's facets, and is important to determine sparkle. The symmetry grade refers to alignment of the facets, and with poor polish, the surface of a facet can be dulled or blurred. Polish gradings are as follows:

  • Excellent (EX)
  • Very good (VG)
  • Good (G)
  • Fair (F)
  • Poor (P)

Now that you understand how the cut of the stone affects its brilliance, you can make an informed decision on important questions such as whether the size of the diamond, or sparkle and brilliance are more important in determining your choice. If you have any further questions please contact us at or speak to one of our experts on our freephone number 0800 043 3573

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