The certification, which should always be based on an appraisal and analysis done by an outside, independent third-party agency, is more properly known as a diamond grading report. This report describes your loose diamonds in terms of weight in carats, clarity of the gems, color and cut. The individuals who perform this service are known as gemologists, and have received specialized training in this particular sub-field of geology. Gemology focuses on the study and analysis of precious stones and gems.

When loose diamonds are accompanied by such a report, they are known as certified. Anyone considering an investment in such diamonds, whether they are or as a hedge against inflation should make sure that their .

The job of a gemologist's certification is not to assign a monetary value on loose diamonds; that happens in the marketplace. However, such a report is used to determine such a value. The weight in carats (a carat is roughly equivalent to .015 of an ounce, or two-tenths of a gram) is the most obvious basis of valuation; however, if the gem has a "cottony" appearance inside, this can affect the value negatively.

SI3 Clarity Scale and the Color Scale. The Clarity Scale was developed by the Gemological Institute of America (GIA); it ranges from "FL" for "flawless" to I3 for "Imperfect," i.e., cracks and occlusions easily seen by the unaided eye.

Colored diamonds are rated on a scale that describes the gems in terms of hue and saturation. They are labeled with a letter of the alphabet from D to Z, ranging from virtually colorless to gems with a deep hue. Diamonds can be almost any color; the color variations include pink, green, blue, purple and amber, and are caused by chemical reactions during the diamonds' formation. Such gems can be worth substantially more than "white," or clear diamonds.

Control of the diamond market is concentrated in relatively few hands, centered around Antwerp, Belgium, where the diamond cutting industry was born over 500 years ago. These wholesalers recommend that diamonds be certified either by the GIA or the American Gem Society Laboratories.

Because of the way the analysis is done, it is impossible to perform a certification on mounted stones; loose diamonds should be certified prior to placement in a setting, ring, or watch, and the seller should provide documentation that such services have been performed.