A diamond grading report or certificate is an independent quality report about a specific diamond. It is issued by a diamond grading laboratory with no affiliation to any retailer, giving the consumer a completely objective opinion on the diamond’s quality. This document includes the exact measurements, proportions, color grade, clarity grade, cut grade and carat weight of the diamond. It also includes specifics that most jewelers do not have the equipment or knowledge to determine such as the diamond's fluorescence, polish, and symmetry*. Each document is numbered, dated, and illustrates the internal and external characteristics of the diamond, otherwise known as a 'plot'.
It is important to note that there is no governing body responsible for the standardization of a diamond report. Each company has the latitude to judge to the standards which they feel are appropriate. For this reason, many laboratories fall in/out of favor depending on how it is being operated. It is also important to know that every grade received has an allowance for deviation. For example, a diamond that has been graded excellent for proportions, polish, and symmetry does not mean that it is 'perfect'. Rather, it refers to the fact that all of those qualities fall under a predetermined standard, which has allowances for error.
The leading diamond laboratories in the world are the Gemological Institute of America (G.I.A.), The American Gem Society (AGS), Forevermark Diamond Institute, and the European Gemological Laboratory (E.G.L.). Any diamond can be evaluated by G.I.A, A.G.S, or E.G.L. for a fee. The Forevermark Diamond Institute tracks the diamond’s source and therefore will not accept diamonds from outside its own supply chain
- GIA (The Gemological Institute of America) established in 1931 and is recognized as the world’s foremost authority in diamond grading. The G.I.A. grades natural, synthetic and treated diamonds. G.I.A. refers to their document as a Diamond Grading Report or a Diamond Dossier (depending on carat weight).
- AGS (American Gem Society) was founded in 1996 with a mission to help protect the consumer by establishing stricter guidelines of diamond grading. They were the first laboratory to establish the ideal cut grade for round brilliant diamonds and features innovative technology that measures the light performance of diamonds. AGS produces both Diamond Quality Certificates and Diamond Quality Reports.
- Forevermark diamonds are graded at the Forevermark Diamond Institute in Antwerp, Belgium. The Forevermark Diamond Institute will only grade natural and untreated diamonds. As a De Beers subsidiary, Forevermark diamonds are sourced from mines that not only comply with their strict political, financial, social, and environmental requirements but also benefit the communities in which they are operating. The Forevermark Diamond Institute refers to their document as a Diamond Grading Report.
- EGL (European Gemological Laboratory) USA’s main office opened in 1977 in the diamond district in New York and has established a reputation of fast turnaround time and fair grading standards and grades natural, synthetic and treated diamonds. E.G.L. refers to their report as a Certificate.
- EGL International founded in Belgium in 1974 and has a presence in most diamond exchanges throughout the world. EGL International is known to be more lenient in their diamond grading. E.G.L. International refers to their report as a certificate.
*Marks Jewelers is equipped with a long and short wave ultraviolet light box as well as a Sarin machine to determine the diamond’s fluorescence, polish, and symmetry.