Colored Diamond Grading

Certified diamonds are graded in laboratories using certain criteria. Some of the most common grading labs include the Gemological Institute of America (GIA) and the International Gemological Institute (IGI). These labs are independently run and provide an expert opinion on quality for loose or unset gems. Most grading institutes have labs or services worldwide and do not sell diamonds. Two types of reports are available: (1) Full Certificates provide full details about a stone including clarity, symetry and polish, and (2) Color-only certificates that provide color grading for natural fancy colored diamonds.
It is not uncommon for dealers to provide a color-only certificate. While the common misconsumption is that the diamond must be of poor quality, this is not always the case. Generally speaking, the vast majority of diamonds are I-SI in clarity. For this reason, diamonds that are able to receive a clarity grading of VS or better are often accompanied with full certificates. This certifies that the diamond is indeed a rarity and provides cause for a premium in price.

A full GIA grading report will contain the following information:

Shape and Cutting Style: Technical term for the shape the diamond was cut into.

Measurements: Dimensions of the diamond in millimeters Lenth x Width x Depth.

Weight: Carat weight.

Depth: The height of a diamond from the culet to the table, measured in millimeters.

Table: The value which represents how the diameter of the table facet compares to the diameter of the entire diamond. So, a diamond with a 60% table has a table which is 60% as wide as the diamond's outline.

Girdle: The outer edge, or outline, of the diamond's shape. The girdle is not graded, but rather it is described by its appearance at its thinnest and thickest points.

Culet: A tiny flat facet that diamond cutters sometimes add at the bottom of a diamond's pavilion. Its purpose is to protect the tip of the pavilion from being chipped or damaged. Most colored diamonds will have no culet.

Polish: Refers to any blemishes on the surface of the diamond which are not significant enough to affect the clarity grade of the diamond.

Symmetry: Symmetry is regarded as an indicator of the quality of as diamond's cut; it is graded as either Ideal, Excellent, Very Good, Good, Fair or Poor.

Origin: Whether or not a colored diamond is of natural or enhanced color.

Grade: Tone of intensity - Faint, Light, Fancy Light, Fancy, Fancy Intense, Fancy Deep, Fancy Dark, Fancy Vivid as well as hue.

Distribution: How evenly color is saturated throughout the diamond.

Fluorescence: The intensity and color of the presence of fluorescence; an effect that is seen in some gem-quality diamonds when they are exposed to long-wave ultraviolet light. Most colored diamonds are not negatively affected by the presence of fluorescence.