Anatomy of a Certificate by Michael Jay 1. Laboratory. While there are a number of aspects and characteristics in a diamond that are easily measured (carat weight, depth, table, etc....), the most important characteristics-color and clarity-are graded by the human eye. This means that you have to rely on the reliability of a human gemologist to determine the very nature of the diamond you have. It is therefore imperative that you buy a diamond that is certified by a reputable laboratory. There are a number of companies that grade diamonds. It is generally accepted that the GIA is the industry standard when it comes to grading quality diamonds of 1/2 carat and higher. The EGL, AGS, and IGI are reputable labs as well, but often lag a grade or two behind the GIA. Please also be careful that the certificate be from the GIA and not from a GIA educated appraiser.Return to top 2. Report Number. This is your diamond's identification number. Every diamond gets a unique number from whoever grades the stone. Sometimes this number is laser-etched into the diamond itself. When this is the case it will be indicated here that it is laser Inscribed. However, don't expect to find it with the naked eye, or even under 10x magnification, as it is microscopic. While there are those that feel that laser inscription gives you peace of mind I tend to be skeptical. First off, if a thief is intent on swapping your stone he can have the same exact inscription etched into your new replacement diamond. Second, you will need 50x magnification to see the laser inscription. This is not something usually not kept handy in your home so chances are you'll never see the inscription anyhow. Return to top 3. Date Issued. This is the date that the certificate was issued. It is not of much indication, as you can always get it re-graded at a later date. If, however, the date is really old, you might want to ask yourself why the stone has been on the market for so long. Return to top 4. Shape and Cutting Style. There are a number of shapes and cutting styles reflected in this. Please see our Shapes page. Return to top 5. Measurements. These are the actual measurements of the diamond from end to end, top to bottom(Length x Width x Depth). This is how the length to width ratio is determined. Length ÷ Width = Ratio. Please see our Ratio page.Return to top 6. Carat Weight. This is the actual weight of the diamond. While it is obviously a very important characteristic of a diamond, please take note of the measurements as well. It is very possible to have a diamond that is .90 carats appear larger than a stone that is 1 carat if it is not cut as deep. Please see our in depth Carat page.Return to top 7. Depth Percentage. This is the percentage of the total mass of the diamond that is in the depth, as opposed to the length/width. This number is the length/width divided by the depth (see measurements). Please see our cut pageReturn to top 8. Table Percentage. This is the percentage of the length/width (from girdle to girdle) that is taken up by the table (see diagram). Please see our cut page.Return to top 9. Girdle. The Girdle is the part where the stone is at its widest and usually its most vulnerable point. If it is extremely thick, it usually takes away from the carat weight that would ordinarily be in visible parts of the stone. If it is extremely thin, it can be easily chipped while being set, especially with a princess cut. They are graded as following: Extremely Thin. Very Thin Thin Medium Slightly Thick Thick Very Thick Extremely Thick. Faceted means it is not smooth, rather faceted like the stone itself. Return to top 10. Culet. The Culet is the very bottom of the diamond. The Culet does not have much of an adverse effect of the diamond unless it is large. If there is a Culet it is considered another facet. They are graded as following: None (perfect point) Very Small Small LargeReturn to top 11. Polish. This is the quality of the polish. Any external inclusion not significant enough to warrant a lower clarity grading will effect the polish grading. The ratings go from Poor Fair Good Very Good Excellent. I would say it is a good idea to stay away from poor and fair. In my many years in the business, I can honestly say that if you place a diamond before me of Good polish or symmetry and Very Good or Excellent polish or symmetry I would not be able to differentiate. Having said that, the industry as of late has been asking a premium for stones that are Very Good and Excellent Polish and Symmetry and according to many standards of ideal Cut grading (ags) the diamond cannot be considered ideal unless it has Very Good or Excellent Polish and Symmetry. Return to top 12. Symmetry. This is a grading of the Symmetry of the Facets. Please see Polish. Return to top 13. Clarity. Please see the clarity pageReturn to top 14. Color. Please see The color pageReturn to top 15. Fluorescence. This is one of the least understood characteristics of a diamond. Under a special blue fluorescent light, diamonds sometimes emanate a bluish glow. It is then graded None Faint Medium Blue (or Yellow or white) Strong Blue Very Strong Blue. There are differences of opinion regarding Fluorescence and I will add my own. I do not pay any heed to diamonds that are Faint or Medium Blue Fluorescent. I've never been able to discern it. On some occasions, especially with lighter stones in D E F range, the strong blue can give the stone a milky appearance visible to the naked eye. There are those that insist that Fluorescence gives lower colored stones a whiter appearance. Return to top 16. Comments. Anytime the GIA has something to add that is not covered in the normal grading characteristics it is added in the comments. Usually, when there are internal or external blemishes (see 17) that are not marked on the diagram they are noted here. When the certificate is a small cert without a picture the flaws are noted here. Return to top 17. This is a map of the actual diamond. Before you go further, the diagram on the certificate is not in any way a representation of the diamond on the certificate. It is just an outline of the facets and all certificates will have the same diagram. The diagram will usually have markings on it showing the nature of the inclusions and where they are located. It does not accurately represent the actual size of the blemish. Please see the Clarity Page. It should also be noted that due to its 2-dimensional nature, unfortunately we can't discern from the certificate how deep the inclusions are nor the color of the inclusion. If inclusions are near the surface then they're more likely to be visible. The same is true if it's a black blemish as opposed to a white one. For that you'll have to call me :).Return to top
