Diamonds come in several popular shapes: round, princess, cushion, asscher, emerald, etc. The round diamond is by far the most known and most popular shape. The most common use for a round diamond is the classic round diamond ring (solitaire ring). In fact, most of today's diamond engagement rings are mounted with round diamonds.
When a round diamond is called a round brilliant diamond, it means that it was cut in a certain way. Today's round brilliant diamonds are have fifty-seven facets (if the culet is flat then 58 facets).
The precise shape of the round diamond has been determined after many years of mathematical researches made in order to achieve as much fire and light from the diamond.
When looking at a gemological certificate (GIA, EGL, IGI, etc.) of a round diamond you will notice that it has three parameters regarding the make of the diamond: Cut Grade, Polish and Symmetry. The grading within these categories goes from poor to fair, good, very good and excellent. To receive the best shine and reflect from a round diamond you should look for the "triple X" round diamond, meaning that the diamond has received an excellent in all three categories. Needless to say that triple x diamonds cost more.
If a round diamond's make is extremely accurate and it's table facet is exactly perpendicular to the pavilion and has excellent symmetry, it may show patterns that looks like eight hearts from the top and eight arrows from the bottom. Keep in mind that it doesn’t necessarily mean that it is the best make, it just means that this particular diamond is in excellent symmetry and that the table is perpendicular to the pavilion. Not all ideal cut round diamonds will have the hearts and arrows effect.