Carat weight is the weight of the diamond measured in carats. One carat is divided into 100 points, so a diamond of 75 points weighs 0.75 carats. Carat weight is the most obvious factor in determining the value of a diamond. But two diamonds of equal carat weights can have very different prices, depending on their quality. Diamonds of high quality can be found in all sizes.
Diamond Clarity is a measure of a diamond's internal flaws and impurities. A diamond that is virtually free of interior or exterior inclusions (commonly reffered to as flaws) is of the highest quality and nothing interferes with the passage of light through the diamond. To determine a diamond's clarity, it is viewed under 10x magnification by a trained gemologist. Small inclusions neither mar its beauty nor endanger its durability.
The diamond color grading scale varies from totally colorless to light yellow. The differences between one diamond color grade and another are very subtle and difficult to distinguish
D-F : Colorless: perfect or almost perfect color.
G-J : Near colorless: good to very good color, and this diamond may "face up" colorless when mounted, especially in white gold or platinum.
K-N : Feint but noticeable yellowish tint.
M-Z : Tinted Yellow
Many people confuse diamond cut with the shape of a diamond. Most diamonds are cut round with a full 58 facets, and a good cut, or make, has more scintillation, more sparkle. Although the cut of the diamond may affect the value of the diamond, the shape, is largely a matter of personal preference and does not affect the value significantly. It is the work of a master cutter that allows the diamond to be cut in such a way as to permit the maximum amount of light to be reflected through the diamond, and that's a great reflection on you. It is the cut that enables a diamond to make the best use of light.