The value of a diamond is determined by its Cut, Color, Clarity and Carat, also known as the classic "Four C's". Understanding such criteria as diamond grading reports and the factors affecting a diamond's cost will help the buyer make a confident and sound decision when making a purchase.
Cut refers to the proportions and shape of the finished diamond, and is the most important factor in determining the brilliance of a diamond. A classic round brilliant cut diamond has 58 facets - 33 on the top, 24 on the bottom and the culet (1 point at the bottom - another tiny facet).
The finished diamond should be symmetrical. The table should be symmetrical, well-centered, and flat, not sloping. The cutlet should be centered when viewed from the top. The crown and pavilion facets should be in exact geometric relation to one another. And, the girdle should be perfectly round exhibiting a straight edge when viewed from the side.
Diamonds that are cut too thin or shallow allow the light to pass through the sides of the diamond and appear lifeless, dull, or flat in the center.
Diamonds that are cut too deep or high do not reflect enough light back through the top of the diamond and appear to be dark in the center.