Most commonly, this term refers to a round brilliant cut diamond (RBC). Brilliant cut diamonds are among the most popular choice for center stones that are used in engagement rings.
The shape of this diamond cut resembles the likeness of a cone. It provides the maximum light return through the top of the diamond.
In round brilliant cut diamonds, the diamond has either 52 or 53 facets. The 53rd facet exists if the diamond has a culet.
An octahedron diamond crystal can ideally produce two round brilliant cut diamonds. This cuts down on the weight loss of a diamond crystal. However, even with modern techniques, the cutting and polishing of a diamond cuts down at least 50% of the diamond crystal.
Shapes included in this category are round, radiant, pear and oval.