One of the unique features of your diamond jewelry is the individual certificate of identity called the diamond grading certificate. Like people/pet animals, your stone's authenticity and individuality are officially confirmed with this certificate.
This is a report given by an independent gemological laboratory. There are many gemological laboratories which hand out these certificates. However, only a few are respected by the whole diamond industry. The most well-known are the European Gemological Laboratories (EGL) and the Gemological Institute of America (GIA).
Each diamond is unique. This individual evaluation is strictly for the diamond's quality, not its value. The certificate maps out inclusions (imperfections), which are hand-drawn. These certificates authenticate the diamond's unique identity since no two stones are exactly alike.
The first information (alongside the issue date of the report) is the Stone ID. This Stone ID is a unique number assigned to your diamond and registered in a global database. Next listed is the diamond's cut and shape. If the shape is different from the standard round brilliant, it is called a fancy shape. (As shown in the sample above).
The dimensions are listed down as [largest diameter n smallest diameter x depth] for the round shapes. The others are listed as [length x width x depth].The weight is listed in carats, the standard unit of weights used for gemstones (One carat is 200 milligrams). The grain lines reflect irregularities in the crystal structure. These are reported as colorless, white, colored or reflective.
The angles and measurements of the diamond that determine its optical properties are duly noted. Table size, crown angle and pavilion depth affect the stone's appearance. The certificate indicates the thickness of the girdle (the outside edge of the stone) relative to the diamond's size, and whether it is polished or faceted. The culet (the stone's bottom point) is listed either faceted or not. If faceted, it is noted relative to the size of the stone.
The grades of the diamond's finish and polish are noted and described including the symmetry. Color is graded, too, from D (colorless) all the way to Z (yellow). Symmetry is the arrangement of the stone's facets (surfaces) and finished angles. Grading reports describe them accordingly, whether they are excellent, very good, good, fair or poor. The cut is listed as well as the quality of the stone's clarity. The clarity is the absence of inclusions (blemishes) and graded from flawless to included based on the size, nature, position, and quantity of the inclusions.
The certificate also notes the pavilion depth (distance from the girdle to the culet) which affects brilliance. Deviations from the Tolkowsky ideal cut are also carefully documented. Most diamonds fluoresce (showing whitish, yellowish, or bluish tint) when exposed to ultraviolet light. They are only stated in the report, not graded. Finally, there is a diagram on the certificate that approximates the shape and cut of the diamond. It has markings (in symbols) that include the type, nature, position, and approximate size of a clarity characteristic.
The EGL mark appears under ultraviolet light. The certificate will ensure that your diamond jewelry has the quality you paid for. Do your diamonds have certificates?