What is a diamond certificate
Properties included in Diamond Reports:
IGI uses the terminology "Diamond Identification Report" although it is recognized as a certificate. Every lab has a certificate (or "report") number, which identifies a diamond uniquely. The Lab keeps an internal copy of everything shown on the certificate, and also additional information. The certificates can thus be re-issued when they are lost.
Shapes can be categorized as Round, Pear, Heart, Oval, etc. Cutting Styles can be categorized as Brilliant, Marquise, Emerald, Princess, Step and Mixed.
Measurements. Measurements of the Diamond's diameter are calculated to the hundredth of a millimeter by a non-contact measuring device or a micrometer which is defined as " minimum - maximum x depth ".
Diamonds are weighed to the thousandth of a carat with a digital measuring device. On the Report, the weight is rounded off to the hundredth of a carat.
The proportions of the diamond can be the summed up as its depth, and its table .Both are expressed as percentage figures. Depth percent refers to the percentage depth of the Diamond, measured from the table to the culet, relative to the width of the stone.
The Table of a Diamond refers to its largest facet, which is the main part of the Diamond you look at when the stone is face-up. Table percent refers to the table size expressed as a percentage of the Diamond's average width. These ratios determine how well a diamond has been cut.
The Girdle of a Diamond is the border between the crown, or uppermost part of the stone and the pavilion, and bottom part of the stone. Girdle thickness is usually expressed as a range since it can vary from thin in one part to thick in another part of the diamond. The girdle can also be faceted. A faceted girdle usually enhances the look of the stone, and includes polished facets into the girdle. Below are example Girdle Thicknesses.
The Culet of a Diamond is the facet on the pointed lower part of the Diamond. Its existence helps prevent chipping. Some diamonds don't have a Culet.
Finish expresses the polish of a Diamond and the symmetrical. and evenness, in the placement of the facets. Polish refers to the quality of the polish given on the facets. An excellent polish shows the care and precision of the Diamond cutter. Symmetry refers to how precisely the facets are aligned to each other.
Clarity ranges from the best grade of IF, down through VVS 1. VVS 2. VS 1. VS 2. SI 1.
SI 2 , I 1. and I 2 until I 3. Clarity expresses the number, size, placement and nature of inclusions and/or surface irregularities on the Diamond. The experienced Diamond Grader at IGI examines the Diamond with the aid of an IGI-Microscope, which aids in identifying the nature of inclusions, and finding pinpoints (very, very tiny crystals inside the Diamond). The actual grade is decided only on what is visible under a 10X magnifier.
Color ranges from the best grade of D, down to Z. After Z we approach the Fancy Color diamonds. Color grades are determined by comparing the diamond with a set of excellent grade stones under special lighting.
Fluorescence refers to a diamonds reaction when exposed to long wave ultraviolet radiations. Too much fluorescence can make a Diamond less desirable.
A Plot is a graphical representation of the imperfections present in the Diamond. Every diamond has unique characteristics like fingerprints. By plotting its characteristics, and combining this with the physical measurements of a Diamond, a Lab can uniquely identify each stone. This plot is a guideline for the Grader in the event that a customer returns to the Lab and requests verification on his diamond purchase. Internal characteristics are plotted in red, and external characteristics are plotted in green.
Comments are used to describe characteristics which are not discussed elsewhere on the certificate, or to mention the items not plotted or shown. For example, "insignificant external details are not shown" is one of the common comments.
All the keywords in the certificate details such as clarity, cut, color, carat, measurement, size etc can be searched at our bulletin board.
Difference between a Diamond certificate and an appraisal
A Diamond Certificate is a document issued by a Gemological Laboratory describing a Loose Diamond. The laboratory will not issue certificates on Diamonds which are set in a mounting. A Diamond Certificate issues a "grade" indicating the physical properties of the Diamond "at the time of evaluation". Furthermore a certificate is a document which retains its value over a long period of time, assuming the Diamond does not chip or is not otherwise altered.
The need of the hour is to differentiate between a GIA GTL (Gem Trade Lab) Grader, and a GIA G.G. or Graduate Gemologist. Many assume that getting an appraisal by a GIA gemologist is the same as getting a GIA Certificate. The GTL (Gem Trade Lab) Grader is a GIA employee who performs the Diamond Grading for the Institute. A GIA Graduate Gemologist, on the other hand, has simply passed the GIA Diamonds and Colored Stone course.Source: www.diamondchatforum.com