Diamonds come in many shapes with the round brilliant cut being the most common. All the others are called fancy shapes. Cutting styles are categorized into three basic types: step-cut, brilliant-cut and mixed-cut.
The mixed cut has both step and brilliant cut facets. In the last 20 years, mixed cuts featuring step cutting on the crown and brilliant cutting on the pavilion have become very popular. Examples of mixed cuts are radiant and princess cuts.
Advice: Deciding on the shape is the first step in the selection process for your diamond. This is probably the most important area where you need to get some feedback from that special person you plan on giving this diamond. If she has her heart set on a princess cut, your surprise marquise isn't going to have the lasting thrill you had hoped for. Go shopping with her and find out what shape she loves.