diamond cut

The cut of a diamond

With this short guide on the cut of a diamond, we continue the discovery journey of the anatomy of the diamond. This informative article follows in the series of our recent blogs covering diamond colour and clarity


Diamonds can be polished in various shapes. The cut refers to the proportions, symmetry and polish of a diamond.

  • Proportions determine the brilliance and the fire of a diamond.
  • Symmetry describes the variation of the different parameters that define the proportions.
  • Polish describes the finishing of the diamond facets.

Whereas the colour and clarity features are intrinsic to the diamond, the cut is a reflection on the craftmanship of the diamond cutter. The grading of the cut is indeed a representation of the skill and precision of the cutter to fashion the facets in such a way that they meet at points and are evenly positioned around the girdle.

cut grade

The values of the cut grading system are:

  • Excellent (EXC).
  • Very Good (VG).
  • Good (G).
  • Fair (F).

The proportions, symmetry and polish are graded separately and listed in the diamond grading report.


Brilliance is a combination of the internal and external reflective effects in a polished diamond. Light entering a diamond is reflected internally on the facets and back out of the diamond. The amount of light that exits the diamond determines the brilliance. When not much light is internally reflected, the diamond is often referred to as a dead stone.


The fire is a measure of the dispersion of light exiting the diamond. The amount of fire in a diamond is determined by the crown height, crown angle as well as the size and number of facets.


Symmetry can be broken down into a number of measurable parameters:

  • Roundness of the stone.
  • Variation in the crown height, pavilion depth, girdle thickness and table width.
  • Central table.
  • Central culet.
  • Symmetry of facets.

Polish is part of the manufacturing process and can include:

  • Scratches.
  • Polishing lines.
  • Burn marks.
  • Laser marks.
  • Extra facets.

An important part of the grading is the size of the diamond, or more accurately its dimensions. These include the maximum and minimum diameter, as well as the height of the diamond. For fancy cuts the dimensions include the length and width.

The dimensions are recorded on the diamond certificate as they are important in assessing the proportion grade. They also serve to identify the diamond.

The cut can be more critical to the appearance of the diamond than the other C’s. A top quality diamond with bad proportions can be less attractive than another diamond with worse clarity or colour but with a perfect cut.

Are you purchasing an item of diamond jewellery and have questions on the cut of a diamond? Contact us on 0845 548 9858 for free, expert advice.

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