When buying a diamond, it is vitally important to know about the 4 C's : cut, color, clarity, and carat weight. Together, the 4 C's determine a diamond's value. It is essential to learn about each of the 4 C's before purchasing a diamond because each C speaks differently to each individual. For some, the carat weight is the most important, while for others, it is the cut.
Cut
To many, cut is the most important of the 4 C's. Each diamond is cut using an exact mathematical formula that unleashes its brilliance and fire. It also refers to the number of facets that the diamond has. The most common cut is the round brilliant. The round brilliant has 58 flat, polished facets that reflect the maximum amount of light. The mathematical formula also takes into account the depth of the cut. If a diamond is cut too shallow or too deep it will lose some of its fire. A well-cut diamond will reflect the light and refract it back out to your eye. Cut is not to be confused with shape.
Color
While diamonds come in every color of the spectrum, the most valuable diamond color is colorless. Truly colorless diamonds are extremely rare and as a result are expensive. They are graded on a color scale established by the Gemological Institute of America (GIA). Diamonds range from D (colorless) to Z. The further down in the alphabet the diamond is, the more yellow it appears. Color can best be determined by looking at a loose diamond on a pure white surface, and by noting any contrast.