The most well-known characteristic of a diamond - Carat is a measurement specific to a diamond's weight. A carat is equal to 1/5 of 1 gram. It is further divided into 100 points for an accurate description of weight.
The following diagram shows the different weights of diamonds - it is important to understand that a 2 carat round cut diamond does not appear to be twice the size of a 1 carat round cut.
Carat weight is an important characteristic, and is certainly influential in the decision-making of most diamond purchases. However it is important to understand that carat weight itself may not accurately reflect a diamond's size. Carat should be considered alongside two other important characteristics.
The dimensions, in millimeters, of the diamond, specifically the distance across the top of the diamond, also known as the table.
Diamonds are primarily viewed from above, and therefore it is important that the dimension of the table is taken into account in any diamond selection, as this reflects the size a diamond will appear when viewed.
The cut grade of the diamond: A diamond's cut grade is an evaluation of a diamond's light performance. The expertise with which a diamond is cut determines its capacity to reflect and scatter light.
The light performance of a diamond shows you how the diamond will look in reality and it will also help you compare it to other diamonds.
When a diamond is cut with the proper proportions, light is returned out of the top of the diamond, giving the diamond its fire and brilliance. A shallow cut will lead to the leakage of light from the bottom of the diamond whereas too deep a cut will cause leakage of light from the sides of the diamond.
The quality of a diamond's cut is widely considered to be the most important of the Four C's in determining the appeal of a diamond. A well-cut diamond enhances the stone, giving an appearance of a larger carat weight, and a greater brilliance.