A diamond’s cut does not refer to its shape or size, but to its symmetry, facet proportions and polishing. The cut of a diamond greatly impacts its brilliance. This means that if a diamond is cut poorly, it will be less luminous. Also, if the diamond cutter chooses to maximize loses brilliance. The beauty of any diamond is largely determined by the amount of white light reflected back to the eye.At ISTANBOULLI GIOIELLI the perfect balance of brilliance.