Color: Diamonds cover the entire spectrum of colors. The majority range from a perceptible yellow or brownish tint up to those rare diamonds described as colorless. Colorless diamonds allow the most reflection of light and are therefore the most desirable. Off-white diamonds absorb small amounts of light, slightly inhibiting brilliance.

Cut: This factor has the greatest influence on the diamond's fire and brilliance. A round, brilliant-cut diamond has 58 facets. When well-proportioned, this shape best shows the stone’s brilliance because it allows the most light to be reflected back to the observer's eye. Stones that appear lifeless or seem dark in the center are probably poorly cut.

Clarity: Most diamonds contain minute traces of non-crystallized carbon and internal stress fractures. Called inclusions, most of these are not apparent to the naked eye but can be seen in loose stones under magnification. Flawless clarity means that no inclusions are discernible when the diamond is examined under a 10X lens.

Carat Weight: The term carat comes from the ancient practice of weighing diamonds against the seeds of the carob tree. The system was eventually standardized, and one carat was fixed at 0.2 grams. One carat is divided into 100 points, so a quarter-carat diamond is 25 points or 0.25 carat. Although carat is a unit of weight, not size, the carat weight of a diamond has come to refer to particular sizes. If properly cut, diamonds of the same weight should be about the same size. These sizes don't apply to other gems, however, because their specific gravities differ from a diamond's.

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