The round brilliant cut diamond is one of the most popular and most researched diamond shape available today, representing approximately 75% of all diamonds sold. Due to the mechanics of its shape, some believe the round diamond has an advantage over other diamond shapes at the proper reflection of light, maximizing potential brightness. For almost 100 years, diamond cutters have been using advanced theories of light behavior and precise mathematical calculations to optimize the fire and brilliance in a round diamond. In addition to being the most popular and researched shape, a round diamond may give you more flexibility in terms of balancing cut, color, and clarity grades while still getting the fire and brilliance you want.