.Put simply, there are four universally accepted characteristics that all diamonds are graded by. They are known as the 4Cs, and they are Cut, Color, Clarity and Carat weight. It is the combination of these four “C’s”that determines a diamond’s value. By changing any of the characteristics, you can dramatically affect the diamond’s value, all other factors being equal.

Understanding Carat Weight

A diamond’s weight is measured in what is known as a ‘carat’, which is a small unit of measurement equal to 200 milligrams. Carat is not a measure of a diamond’s size, since cutting a diamond to different proportions can affect its weight. (The word ‘Karat’is used to express the purity of gold, and is not used in relation to diamonds.) Here is a diagram that shows the relative size of various carat weights in a diamond that is cut to the same proportions:

Note: the diamonds illustrated are not shown actual size.

The most important thing to remember when it comes to a diamond’s carat weight is that it is not the only factor that determines a diamond’s value. In other words, bigger does not necessarily mean better. All four Cs—Cut, Color, Clarity and Carat Weight must be balanced in order to arrive at a diamond that fits your budget. None of the 4Cs is mutually exclusive, nor is any one more important than the others.

Understanding Color

The most important thing to know about color when it comes to diamonds is, in general, the less color a diamond has, the more valuable it is, all other factors being equal. Diamonds are found in nature in a wide range of colors, from completely colorless (the most desirable trait) to slightly yellow, to brown. So-called ‘fancy color diamonds’come in more intense colors, like yellow and blue, but these are not graded on the same scale.

The color grading system for diamonds uses the letters of the alphabet from D through Z, with ‘D’being the most colorless and therefore the rarest and most valuable, and ‘Z’having the most color within the normal range, and being the least valuable, all other factors being equal. A diamond’s color is determined by looking at it under controlled lighting and comparing them to the Gemological Institute of America’s color scale, which is based on a set of diamonds of known color. Here is a diagram showing how a diamond’s color is graded: