THE 4 C'S
Cut
The cut of a diamond refers to the symmetry and the proportions of the diamond. The cut gives the diamond its sparkle. Using the measurement of the proportions and angles of a diamond experts can calculate the light presentation of a diamond.
Color
The color of a diamond is perceived as a critical factor that determines the overall beauty of a diamond. Colorless diamonds are the most desirable and the most valuable diamonds. The customary color grade system is comprised of letters from D to Z. D-F are considered colorless, G-I is near colorless or white, J and below with show traces of yellow to brown as you go down the alphabet.
Clarity
Diamonds have small imperfections in them called inclusions. The more inclusions there are in a diamond, the less valuable the diamond will be. Internally flawless is the best and quite rare followed by very,very slight imperfections (VVS), very slight imperfections (VS), slightly imperfect (SI) and imperfect (I).
Carat weight
The measuring unit for the weight of a diamond is carat. One metric carat is exactly 200 milligrams or 1/5 gram. The origin of the word carat is from the carob seeds that were used to balance scales in antiquity.