Anyone who has ever shopped for a diamond before might have heard the mention of the "4C's" - color, clarity, carat (or carat weight), and cut. These four characteristics that determine a diamond's rarity and value. Understanding them can help you understand why diamonds of equal size may not be of equal value. The many different ways that each of the 4C's can be combined that is the key to understanding what makes each diamond unique and valuable.

While most diamonds appear to be white, virtually all have slight traces of color. Evaluating a diamond's color for grading purposes is done by measuring the degree to which a diamond approaches colorlessness. Gemologists and Jewelers describe the color of diamonds on a letter scale beginning with D (colorless) and moving through the alphabet to Z. The degree of colorlessness is not easily discernible to the untrained eye. D, E, and F color grades are more expensive because they are more rare. However, well cut diamonds with good clarity of all color grades can be equally dazzling as it is the inerplay of the 4C's which determines each individual stone's uniques beauty. Deeply colored diamond in shade such as pink, blue, and yellow are known as "fancies" and are especially rare and valuable.

Practically all diamonds contain naturally occurring internal blemishes called inclusions, or a diamond's natural birthmarks (these can look like tiny crystals, feathers, or clouds.) However, many are microscopic in nature and can only be glimpsed under powerful magnification through a standard 10-power jeweler's loupe. Diamonds with the fewest inclusions are graded VVS1 or VVS2; those on the other end of the scale are graded I1 or I3. The fewer inclusions the rarer the stone.

Carat indicates the weight and therefore the size of the diamond. One carat weighs 0.2 grams, or 1/142 of an ounce. Jewelers, however, refer to stones using points: 100 points equal 1 carat; 50 points, a half-carat; 25 points, a quarter-carat and so on.

Cut is perhaps the most important of the 4C's because a quality cut is what helps to unleash a diamond's fiery sparkle. A well cut diamond, regardless of shape, releases the fire and brilliance of a diamond through the proportion of its 57 or 58 facets (tiny planes that create angles), allowing the maximum amount of light to be reflected through the diamond. In order to maximize this fire and brilliance, a diamond cutter must place each of the stone's facets and angles, which act as light-dispersing mirrors, in exact geometric relation to one another. Diamonds that are not cut to proper proportions (too deep or too shallow) lose light that spills through the side or bottom.

Cut is also quite different than shape. While cut is a technical quality, determined by the skill of the diamond cutter, the matter of shape is a personal choice. The round (brilliant) is often the most popular of all shapes, with the majority of brides-to-be recieving a round stone. Other popular and traditional shapes include the marquise, pear, oval, emerald, princess, and heart shape.