The Four C’s To Diamond Quality
COLOR: The most valuable diamonds are completely colorless. These diamonds are known as “white” diamonds in industry parlance. White diamonds are rare, but most possess a slightly yellow or light brown tint. The more obvious the coloration, the more the value decreases.
CUT: The purpose of cutting diamonds should be to achieve maximum reflection, making all light refract and reflect through the top of the stone. Unfortunately, in attempting to cut as large a finished gem as possible from the raw diamond form, cutters can create diamonds that are too shallow or too deep for best radiance. When looking at round diamonds, Ideal Cut and Premium Cut diamonds are usually preferred for their symmetry and excellent light dispersion.
CLARITY: Because they are formed naturally, it is extremely rare to find a diamond with no internal flaws. These internal flaws are called inclusions. Most inclusions are not visible, except under magnification. The size, location and number of these inclusions, determine its clarity grade and cost.
CARAT WEIGHT: Diamond weight is measured in carats (compared to "karats," a measure of a metal's purity). A carat equals about 1/5 of a gram, and is divided into 100 parts, or "points”. Therefore, a 150-point diamond, would weigh 1.5 carats.
While carat weight is the most frequently cited of the "four C's," it is by no means the most indicative of its worth. A diamond with superior clarity, cut, or color can be worth much more than a larger stone.
For more information on understanding diamond quality, please visit the Gemological Institute of America's 4Cs Education Page.