The cut is considered to be the most important characteristic of a diamond’s appearance, greatly affecting how it reflects light- or how it sparkles. When assessing a particular diamond, you should consider how well proportioned it is first and foremost. Good to excellent cut stones are well proportioned, allowing light to reflect off or enter through the diamonds surface. Poorly cut stones have unequal proportions and as a result, have diminished light performance. Instead of light striking through the surface and reflecting back to the viewer’s eyes, light actually leaks out of the bottom of the diamond if cut too shallow, or breaks through the side if cut too deep.
Aside from reflecting light more effectively, a well cut stone can actually appear larger due to its increased diameter, as opposed to a diamond that is cut too deep.
Brilliance, Dispersion, Scintillation
A precisely cut diamond will produce the best light return, which comes in the form of brilliance, dispersion and scintillation. Brilliance is the total light reflected back to the eye from a polished diamond’s surface or light reflecting from a diamond internally. Dispersion occurs as light travels into a diamond, separating white light into its spectral colors. Now, as you move a diamond or a light source around a diamond, you will see flashes of color. The flashing or sparkling of light is referred to as scintillation. If a diamond exhibits all three of these characteristics, it is most likely a well cut stone and is of great value.