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Anatomy of a GIA Certificate

The GIA diamond grading report is a simple, straightforward document which represents decades of concentrated effort to create a grading system which imparts as much information as possible and is reproducible to a degree that it makes the most discerning diamond dealer satisfied. It is the pedigree that goes with the diamond. It is also very important to have because in case of a loss, the insurance company must replace the stone with like kind and quality - another certified stone. You do not have to be at the mercy of your jeweler in this situation.
  There are several parts to the document:
GIA Certificate Sample

1. An original GIA diamond grading report will have the Gemological Institute of America logo in the upper left. GIA GEM TRADE LABORATORY will be at the top of the document, with addresses and phone numbers, and the document will be laminated.

2. The report will have a number. The position of this number will vary depending on the date issued. Recent documents have the number in the upper left hand corner under the GIA logo. Below that number will be the date of the document. Other places in which the report number will appear will often be to the right of the centered "DIAMOND GRADING REPORT" just below the addresses and the phone numbers of the lab. Phony GIA certificates are known but THEY ARE QUITE RARE AND UNUSUAL. Very old certificates may have an LA or NY in front of the number. This indicates whether the document was created in the Los Angeles office or the New York office.

3.Shape and Cutting Style:

This will tell you the type of cut. Possibilities include round brilliant, pear brilliant, oval brilliant, emerald cut, and heart brilliant. Two of the most popular cuts today are the radiant and princess. The GIA refers to these cuts as "cushion octagon modified brilliant" and "rectangular modified brilliant" respectively.

4.Measurements:

Measurements are made in millimeters to the hundredth of a millimeter. The measurements are taken 3 ways; length, width and depth. This is one of the two most important items for making sure the diamond matches the certificate. The chances of getting two diamonds that have the same measurements to the hundredth of a millimeter for all three dimensions is astronomically low. Couple this information with the plot of inclusions provided on the document, and the matching of stone and certificate becomes easy.

5.Weight:

The weight of a diamond is expressed in carats. 144 carats equals one troy ounce. A carat is divided into 100 points. Therefore a 25 point stone is .25 carat. A 75 point stone is .75 carat, and so on. The heavier the stone, the rarer the stone. In a specific quality, a larger diamond will cost more than a small one. Prices increase on a per carat basis tremendously as the carat size increases up to five carats. Stones larger than 5 carats increase on a per carat basis more slowly above five carats. In fine stones, however, the per carat price is so high that the addition of one or more carats over five can escalate the total price of the stone tremendously.

6.Proportions:

This section describes the proportions of various parts of the diamond in relation to other parts of the diamond.  The Depth % tells how deep the stone is in relation to the diameter. In some cases, and depending on the cut, a stone may be too deep or too shallow to bring out maximum brilliance. The actual acceptable depth % varies from cut to cut so it is important to talk to an expert about the particular diamond you are considering. Round stones have much tighter acceptable standards than do fancy shapes.  The Table % is the percent that the flat top facet called the table takes up against the diameter of the stone. Again, acceptable table percentages vary according to the cut, but the round has the tightest acceptable standards.  The Girdle is the thin rim that separates the top or crown of the stone from the pavilion or underside of the stone. This rim may be unpolished or faceted. It may have a "natural" which is a small portion of the outside of the rough diamond on it. It may be thin to extremely thick. Thin to thick is usually acceptable.  The Culet is the little facet on the very tip on the bottom of the stone. Some stones don't have a culet some have large ones (often on old cuts like Old European or old mine cuts). Large culets that can be readily seen with the naked eye are generally considered unacceptable.

7.Finish:

These two grades indicate the grade of the polish and the symmetry of the stone. The polish of course is how well the stone is polished and a main consideration in that grade is the absence of polishing marks - normally seen under magnification. The symmetry indicates how well the facets in the top of the stone line up with the bottom facets. In very fine stones, it is preferred for both to be good, very good, or excellent. Fair is sometimes acceptable in symmetry but very seldom acceptable in polish.

8.Clarity Grade:

The clarity grade will always be given. See our section on the basics of diamond grading for more details.

9.Color Grade:

The color grade of the stone will always be given. See our section on the basics of diamond grading for more details.

10.Fluorescence:

About one out of every ten diamonds glow in ultraviolet light. Most glow blue, but other colors may occur including yellow, orange and green. Blue fluorescence is usually a plus for white stones, so long as it is not too strong. Yellow, orange, pink, and green are usually a detriment for white diamonds, but a strong yellow fluorescence in a fancy yellow diamond is a positive attribute. By and large, most fluorescence is just another form of identification of the diamond and does not effect the value.

11.Comments:

This space is reserved for things that the laboratory wants you to know but they do not fit into the format of the report. Most comments are minor and do not impact the value of the stone.

12.The Plot:

The plot of the diamond shows both the significant internal inclusions and the externally important items which are evident under 10 power. Again, the plot is the most significant thing that will match the stone to the document.
 
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