A diamonds cut is often confused for its shape, however the cut grade refers to how well a diamond returns light through the table (top) of the diamond into the viewers eye. An excellent cut diamond will have more brilliance and fire than a poorly cut diamond; this is because, an excellent cut stone is able to reflect light through the table of the diamond more effectively. A poorly cut diamond will reflect some of the light out of the sides or bottom of the stone, which means that it will have less life and sparkle.

Brilliance, Fire (Dispersion) & Scintillation

There are three types of reflection to a diamond, which together form what is commonly known as 'sparkle' these include: brilliance, fire (dispersion) and scintillation. When light hits a diamond its generally acts in two ways, either it will reflect out of the table of the diamond into the viewer's eye, or it will enter the diamond and scatter.

Brilliance is when the light enters the diamond and reflects directly out of its table. Fire or dispersion occurs when light enters the diamond and disperses. Here the white light is split into its individual wavelengths, which is why flashes of colours are seen in a diamonds sparkle. Scintillation refers to the flashes of light which are reflected from a diamond when it's moved. 

How the Diamond Cut is Assessed

The diamond cut is assessed by evaluating the symmetry, polish and proportions of a diamond to give the most stunning balance of all three types of reflection.

The cut grade is based on a diamonds ability to reflect and refract light. A top quality diamond will have excellent, symmetry, polish and cut to ensure that the diamond is able to reflect and refract light for maximum brilliance, fire and scintillation.

Diamond Cut Grades 

 

Excellent

An excellent cut grade is exquisite and rare, these diamonds have been cut to optimum proportions to return the most amount of light possible back through the table of a diamond. An excellent cut diamond will be priced higher than a diamond of the same carat size with a lower cut grade.

Very Good

This cut tends to be slight lower in price than an excellent cut diamond. A very good cut diamond will reflect nearly all of the light that enters the diamond, just not quite as much as an excellent cut. 

Good

This cut grade reflects most of the light that enters the diamond, but less than a diamond of a very good cut. These diamonds are generally priced lower than than a very good cut diamond of the same carat weight. 

Fair Cut

A fair cut diamond will not have as much life and sparkle as a diamond which has a good cut grade or higher. 

Poor Cut

Poor cut diamonds are usually so deep or shallow that only a small amount of light is returned through the table of the diamond.