Shape

Diamonds are available in a variety of shapes, not just round!
Throughout history, the shape of a finished diamond has taken on many provocative and seductive forms. The term "shape" in reference to diamonds is often confused with the technical term "cut". The precision and delicacy with which your diamond is cut will determine its brilliance, its fire, and its ultimate beauty. The shape you select is a matter of individual taste, and today your choice is only limited by the skill and imagination of the craftsman.
A shape other than a round brilliant cut is referred to as a fancy cut. Some of the most common fancy cuts are princess, marquis, and oval. Each cut requires a specific mathematical formula to produce the desired result. For example, a marquise diamond usually has a 2:1 ratio for its cut, which means the length is twice the width. A slight variation to this formula can produce a cut that is either thinner or wider than the average, depending on what is desired. The ratio for an oval cut is usually 1.5:1, and the ratio for a heart cut is usually 1:1.

Questions often arise as to the differences between the extremely popular princess cut diamond and the less often seen radiant cut diamond. The most noticeable feature that distinguishes the princess from the radiant cut is that the radiant has the corners cut off, creating an eight-sided figure, whereas the princess has sharp, pointed corners and is four-sided. Although they appear similar, they are technically two very different cuts. Both cuts come in square and rectangular (elongated) forms. A common misconception is that the radiant is rectangular and the princess is square. For both, a ratio of 1:1 is square, and a 1.3:1 is considered rectangular.

The emerald cut is often reserved for those diamonds that possess the high clarity required for it. Due to the relatively low number of facets of the emerald cut, inclusions are often visible that ordinarily would not be seen in any other cut. Therefore, most gem cutters reserve the emerald cut for those specimens that have few inclusions, in order to avoid highlighting any flaws. The most common ratio for this cut is 1.5:1.