When determining the value of a diamond, the 4 C's are often what affects the price. These 4 C's are: Carat, Color, Cut and Clarity. While each of these are important, and can have a dramatic impact on the overall price, a diamond's cut alone can alter its value by over 50%. In the most popular diamond design, a circular shape, the cut is what provides that deep sparkle and gives a diamond its beauty. Diamonds under a magnifiying glass When most people hear the word "cut" in reference to a diamond, they often believe that this refers to the shape of the stone. This is incorrect, as the shape of the diamond is used to determine the cut. The shape of a gem simply refers to the different contours of the stone, while the cut tells you how well this design was actually performed. A diamond's cut is the style, or design, used by jewelers when they are shaping the stone in order to polish it. The way the stone is cut is typically a reference to the proportion, polish and symmetry of the gem.  As Diamond Whisperer explains, these factors are what is used to determine a diamond's brilliance, which ultimately decides the price. Hence, a poorly cut gem will be less valuable. The design of a diamond is often what makes the diamond so desired. This will affect how the stone sparkles and shines in the light. The design of a diamond is divided into two separate parts. The crown of the diamond is the top portion which will rest facing up when fitted into jewelry. The crown of the gem should be roughly on third of the stone's overall length. The other part of a diamond is the pavilion, which should be twice the size of the crown. These proportions will be displayed on a diamond's certificate during the time of purchase.   As many people think a diamond's value is determined primarily by its size, or carats, they tend to overlook what actually gives the diamond its sparkle. If the diamond is cut improperly, the end result would be a less brilliant, less luminous stone, regardless of its size.