Cut is the most visible because it's what makes each diamond sparkle, and influences your diamond's shape.
Cut refers to a diamond's proportions, finish, symmetry and polish. It's how a diamond- in-the-rough becomes the beautiful gemstone you can't wait to show your friends. The cut is directly responsible for just how good your diamond is going to look-and how good you're going to look wearing it.
A diamond with precise cuts and shape will sparkle and shine because its many facets catch the light perfectly. Like little points of light dancing on your finger. Ahhhh.
As an example, look at this round brilliant cut with 58 facets. Since the diamond's beauty directly reflects the quality of the cut, the precision with which the facets are arranged is of prime importance. They determine the amount of light reflected to the eye, which we call brilliance. And if your man is smart, he's over on his side taking notes.