Of all the 4 Cs, cut has the greatest effect on a diamond's beauty. In determining the quality of the cut, the grader evaluates the cutter's skill in the fashioning of the diamond; technology assesses the diamond's light performance. The more precise the cut, the more captivating the diamond is to the eye.
Gem-quality diamonds occur in many hues. In the range from colorless to light yellow or light brown, diamonds are compared to Master Color-Comparison Diamonds under controlled conditions. Colorless diamonds are the rarest. Other natural colors are known as fancy. Their color grading is unique.
Diamonds can have internal characteristics known as inclusions or external characteristics known as blemishes. When grading clarity, the grader uses magnification and specific lighting and considers the effect these characteristics have on the diamond's appearance and/or durability. Diamonds without inclusions or blemishes are rare; however, most characteristics can only be seen with magnification.
The carat is the diamond's physical weight measured in metric carats. One carat equals 1/5 gram and is subdivided into 100 points. Carat weight is the most objective of the 4 Cs. It involves no estimates, comparisons or judgments.