A certificate is also useful for identification purposes in the future. For example, in the case of a lost or stolen diamond, a certificate will facilitate its replacement with a diamond of equivalent quality.

Here's what to look for in a reliable diamond certificate:

Date of the report: It's possible that the diamond has been damaged since the report was issued. Ask your retailer to show how your diamond matches with the certificate offered.

Unique identification number: EGL USA offers consumers an easy on-line verification of their individual certificates. Very often the ID number will be laser inscribed on the diamond. If not, you can ask your jeweler to have it done. All certificate numbers issued by The EGL USA Group are preceded by either "US" or "CA," depending on whether it is issued in the U.S. or Canada.

Issuer of the report: Make sure that the issuer is an independent, well-established and respected laboratory.

Origin:  Look for a statement attesting the origin, i.e., whether it is a natural diamond or it has been enhanced. Labs do not grade fracture-filled diamonds. However, reports are issued on laser-drilled diamonds.

Carat weight: An exact measurement must appear on the report.

Shape and cut: Shape, such as round, pear or oval, and cutting style, such as brilliant or step cut, are noted on a certificate.

Measurements: Major laboratories measure diamonds in millimeters, typically to the hundredth of a millimeter. Exact dimensions are very important in identifying a diamond, as it is unlikely that two diamonds will have identical weight and dimensions.

Proportions: Good proportion--particularly the depth and table percentages--influences the brilliance and fire of a diamond. In fact, proportion is as important as color and clarity grades.

Clarity and color grades: Most diamond buyers know their 4Cs: cut, color, clarity, and carat weight. 

Fluorescence: Some diamonds will appear to exhibit different colors in ultraviolet light. This property is called "fluorescence."  Click here for more on fluorescence

Take the time to understand how to read a certificate, however, your diamond purchase should not be based solely on this document. It cannot replace a visual inspection of the diamond you are considering. Some diamonds are beautiful even if they don't look good on paper.

Finally, remember that diamond certificates are not guarantees, valuations or appraisals. While professional labs employ experienced well-trained graders and use the most accurate gemological instruments to grade gemstones, laboratories make no warranties regarding the accuracy of their certificates. Diamond grading, like diamond cutting, is both an art and a science.