Diamond Cut Grades
Choosing a well-cut diamond is arguably the most important of the 4Cs. The cut determines the shape and sparkle of a diamond, and it contributes to the fire (colourful flares), brightness (light reflecting off the top) and scintillation (flashes of light). Standards have been developed of cut grades to evaluate colour and clarity but also the structure of a diamond. A well-cut diamond will have many more facets than a poorly cut diamond and will also have ideal diamond proportions to maximise light performance. This is about finding the right relationship between the width of the top (surface table) and the depth of the diamond. A diamond that is too deep or too shallow will allow light to leak through rather than be reflected back out.
Also known as Ideal Cut, they have been proportioned in such a way so as to maximise the light refraction potential. Thereby providing that fiery sparkle that sets these stones out from the rest.
The cut and shape of these diamonds allows a good amount of light to travel back out from the upper surfaces of the stone. This still allows for scintillation and sparkle but not as much as an excellent or very good cut diamond. These stones are more shallow.
With a fair cut diamond most of the light is lost to the sides and does not refract back out through the uppermost surfaces. These stones are generally quite thick and deep and hence have smaller tables as compared with good or better cut stones
Whilst a diamond may have a very good colour and clarity, the sparkle will be lost if the light cannot refract back out of the top surface of the diamond due to a thick or deep cut. In this case most of the light will be lost from the bottom of the stone.