Cut.
Cut is perhaps one of the most important aspects of a diamond. The way a diamond (or other precious or semi-precious stone) is cut, determines the way light passes through to efficiently reflect the diamond’s beauty. A high level of accuracy and much skill is necessary to successfully cut a beautiful diamond. When looking at a diamond, you will want to see a considerate amount of light being reflected throughout the stone.

Color.
Diamonds that are truly colorless are extremely rare; many times yellow or brown can be seen in the stone and these subtle differences in color can have a rather large impact on its value. A well cut diamond has the ability to refract and disperse light that will disguise some traces of coloration. Some sought-after colored diamonds are available and are considered to be fancy in color; such diamonds include any color other than colorless to light yellow or brown. In most circumstances, you will want to find a diamond that is as near-colorless as possible.

Clarity.
Clarity is the evaluation of a diamond's internal and external characteristics in terms of inclusions. Inclusions are areas within the stone, such as crystals and breaks, which take away from the visual beauty of the stone. Blemishes are found on the surface of the stone and include deep scratches, breaks and chips. When looking for a diamond, you will want to find a stone that has little or no inclusions and no exterior blemishes.

Carat Weight.
The standard measurement for diamond weight is the carat. A carat equals 1/5 of a gram (or 1/142 of an ounce). Each carat is further divided into points, each point representing 1/100th of a carat. When choosing a diamond, carat weight is considered to be one of the least important aspects because a larger stone does not mean that it is high quality. When looking for a diamond, remember that quantity does not necessarily mean quality.

The following chart will help in determining the quality of a diamond: