A half carat is 50 points and is written as 0.50 cts., and so on. The carat has a standard metric weight of 0.2 gram. The size and weight of a diamond have no bearing on a diamond's cut, clarity or color. Most diamonds of gem quality vary in shade from colorless to yellow. To determine color, diamonds are compared to an internationally accepted set of stones ranging from D, colorless, the highest color grade a diamond is awarded to Z, the yellowest.
Diamonds also occur in colors such as brown, orange, pink, etc.
Strong natural colors like blue, red, pink and canary yellow are rare and, therefore, very costly. Visible carbon inclusions will lower the clarity rating. Very Slightly Included. VS1, VS2 Very Slightly Included. Inclusions and external blemishes difficult to locate under 10x magnification.