Fine jewelry is an investment that can last for generations, so it's important to know how to buy diamonds before you start shopping. When purchasing diamond jewelry, pay attention to the four C's: color, clarity, cut, and carat weight. These are the four characteristics by which a diamond's quality is measured. If all four are ranked high, the diamond jewelry will cost more, but it will be that much more beautiful and valuable.
Diamond color is actually graded on lack of color. The best fine diamond jewelry contains stones that are almost clear. The hues graded in "white" diamonds are actually faint tones of yellow, brown, and grey. An alphabetical scale from D through Z is used to rank the color. Imagine two glasses of water -- one clear, the other containing a few drops of lemonade -- and you will begin to get an idea of the differences in diamond color grades. The following color scale is an approximate representation of color saturation in diamonds (click to enlarge):
Fancy color diamonds: Once the color saturation moves beyond Z or has a completely different hue than yellow, brown, or grey, the gem then becomes a fancy color diamond. Fancy colors are graded on how much color the diamond has and how strong the hue is. Diamonds come in every color of the rainbow, including blue, pink, yellow, purple, and black. In general, fancy diamonds are rarer than white diamonds.
Clarity describes the inclusions and blemishes of a diamond. The fewer inclusions and blemishes a diamond has, the more valuable it is. Clarity can also have a direct impact on the stone's brilliance: Inclusions in the diamond can block the light from reflecting inside the stone, which is the feature that gives diamond jewelry its fiery beauty. The following diamond clarity grades are listed from best to least and are based on the observations of trained gemologists (click to enlarge):
Cut is divided into shape, proportion, polish, and symmetry. Shape and proportion are all of great importance when cutting a diamond to its best appearance. Shape and proportion determine how a diamond scintillates because it affects how light is reflected and refracted inside the stone, which is what causes diamonds to sparkle. Depending on how deep or shallow the diamond is cut, the face-up appearance of the diamond can also vary greatly. The polish describes how well light enters and exits the facets of the diamond. Symmetry can describe both length-to-width ratio and also depth percentages.
Shopping by shape: Jewelers use a standardized set of shapes as patterns for cutting stones. The shapes with more facets, like the 58-facet round brilliant, have the most sparkle, but the shapes with fewer facets, especially the emerald, better showcase the color and clarity of higher quality diamonds. Shape is especially important in diamond rings. The princess, heart, and round shapes flatter delicate fingers, long or short, and the longer shapes, such as marquise, pear, and emerald, elongate the finger. You can read more about each shape in our diamond cuts fact sheet.
Carat is a weight measurement of diamonds. One carat is equal to 0.2 grams. It is abbreviated "ct" or "CT" when describing a single stone. "TDW," meaning "total diamond weight," is added when the diamond jewelry is set with multiple diamonds. For example, a solitaire diamond engagement ring may be described as 1ct while a three-stone diamond anniversary ring would be 1ct TDW. This chart shows how the sizes compare to each other, but this is not a representation of the actual size of diamonds (click to enlarge):
Carat vs. karat: Carat is not the measure of gold's purity, which is spelled "karat" and is abbreviated "k." You may have a 1-carat diamond in an 18-karat gold setting.