Diamonds are renowned for their ability to transmit light sparkle intensely. We often think of a diamond’s cut as shape (round, emerald, pear), but a diamond’s cut grade is really about how well a diamond’s facets interact with light. Precise artistry and workmanship are required to fashion a stone, so its proportions, symmetry, and polish deliver the magnificent return of light only possible in a diamond. A diamond’s cut is crucial to the stone’s final beauty value. And of all the diamond 4Cs, it is the most complex and technically difficult to analyse. To determine the cut grade of the standard round brilliant diamond – the shape that dominates the majority of diamond jewellery –the laboratory carrying out the certificate calculates the proportions of those facets that influence the diamond’s face-up appearance. These proportions allow the assessor to evaluate how successfully a diamond interacts with light and to create desirable visual effects such as: Brightness: Internal external white light reflected from a diamond Fire: The scattering of white light into all the colours of the rainbow Scintillation: The amount of sparkle a diamond produces, the pattern of light dark areas caused by reflections within the diamond The diamond’s cut grade also takes into account the design and craftsmanship of the diamond, including its weight relative to its diameter, its girdle thickness (which affects its durability), the symmetry of its facet arrangement, and the quality of polish on those facets.