The beauty and brilliance of a diamond lie between the balance of its cut, the symmetry of the facets and the perfection of its proportions. A perfect cut allows a better refraction of the light and gives the stone stunning sparkles. The cut needs to be differentiated from the shape of a diamond.
The light that enters the diamond is slowed down and illuminates the stone, while fires and flicker are due to the refraction of the ray of light on many points inside the stone.
A too deep, too thick or too flat cut will cause the light to pass through the diamond and make it lose its luminosity.
Passage of light through the stone (white) and refraction of the ray (spectral colors)
The 3 elements to observed:
Fires / dispersion
Cut ranking by GIA :
Very Good - Very Good (VG)
Good - Good (G)
Fair - Fair
Mediocre - Poor (P)
Diamonds Hearts & Arrows
A round brilliant diamond has 57 facets. If all those facets are in harmony, it will result in a perfect pattern of eight symmetrical hearts when the diamond is seen from the bottom and eight symmetrical arrows when it is seen from above.