First
and foremost, the first item to look for when researching a diamond is
which lab evaluated and wrote the report for the diamond. You should
note that grading accuracy is not always consistent between gemological
laboratories. Because of individual judgment some inconsistencies may
occur in assigning quality grades. These inconsistencies are often the
result of diamonds on the line between two grades. Fortunately,
diamonds rarely vary over one grade between labs, despite what many
jewelers would have you believe. As it stands, the only legitimate labs
in order are: the Gemological Institute of America GIA, The American Gem Society Laboratories AGS, the US division of the European Gemological Laboratory EGL US, the international division of the European Gemological Laboratory International EGL, Hoge Raad Voor Diamant (Diamond High Council, Belgium) HRD, the International Gemological Institute IGI, and Accredited Gem Appraisers AGA.
G.I.A.
was the first diamond grading lab that began certifying diamonds and is
still the most well known and respected laboratory in the world. Since
GIA, AGS Labs, EGL USA, EGL, HRD, IGI,
and AGA have begun to offer features GIA doesn’t. If all of these labs
offered the same features as GIA and had as stringent guidelines, there
would be no point in using an alternative, as a potentially lower cost
for the report would be outweighed by the value associated with a GIA
diamond.
Many manufactures and
mines, however, weren’t able to send their diamonds to GIA labs at
first and therefore, to this day, only deal with EGL and HRD. EGL has
been known in the past to assign a higher grade on diamonds that have
grades on the border between two grades. GIA will usually assign the
lower grade. EGL used to have a very poor reputation as they did this
consistently until they lost many manufacture’s business to GIA and the
US division, EGL-USA. Manufacturers were sending their diamonds to the
US to have them graded by GIA and EGL USA rather than EGL in their own
countries, and EGL has since been forced to follow suit. Jewelry stores
in Europe usually deal with IGI. Accredited Gem Appraisers, AGA,
although they are not nearly well known, are the first lab to offer cut
grades on fancy diamond shapes. They have actually been around for over
100 years. Global Gemological Laboratory, GGL,
has the highest quality out of the less-than reputable reports and
appears to have been developed specifically for several supermarkets
like Costco, Reeds, Kay Jewelers, Jared, and the e-tailer, Yehuda
Diamond Co.
There are literally
hundreds of illegitimate labs that issue grading reports and
certifications, many of which can be found on eBay. We personally tried
to visit NGL’s (National Gemological Laboratories) office at 132 West
36th Street, 8th Floor New York, NY 10018 to discover that they weren’t
there. Many of these illegitimate labs change their addresses
constantly.
Robert Shipley,
the founder of GIA, actually managed to improve upon GIA’s grading in
establishing The American Gem Society. Originally, since members of AGS
had no way of indicating a superior cut on a grading report, AGS began
to offer cut grades on their own reports in 1996 as a numerical system ranging from 0
to 10, based on a diamond’s table percentage, crown angles, pavilion
depth, culet, and girdle. The AGS system of defining cut grade is
modeled after the 1919 Tolkowsky theoretical well-proportioned brilliant based on 17 major facets or
surfaces, which is a standard of American “ideal” cut diamond
proportions to this day.
Since AGS began issuing cut grades, GIA has followed suite with their “Excellent” cut grade. GIA bases their cut grade on brightness, fire, scintillation, weight ratio, durability, polish,
and symmetry or a hearts & arrows pattern or lack thereof. Although
GIA looks at more factors, they take averages and not exact figures,
which works on a perfectly symmetrical diamond like a Hearts and Arrows
Round Brilliant cut, but isn’t as accurate if the diamond has some
slight inconsistencies. On the other hand, GIA has included sufficient
minor facet information on each diamond to provide a more thorough
exam, as they have accepted the importance of minor facet cutting in a
diamond’s overall appearance.
Grading Report Glossary
Every lab has different skills and policies. Most smaller gem labs are extensions of local jewelry stores, created solely for the purpose of raising the image of the inventory owned by a store. Such labs are hardly unbiased and the certificates are rarely accurate. To make it simple, if you want an honest assessment of the true quality of a diamond, avoid any lab except the ones listed above.
GIA: Gemological Institute of America
The most widely respected laboratory in the world today. Grading Reports from this lab are in such demand that diamonds with a GIA cert are often priced 3-5% higher. The price is also due to the fact that the diamond is truly the stated quality, since GIA is known for its reliability and conservative grading. All labs can make a mistake, but GIA labs are truly unbiased and among the most conservative and consistent.
AGS: American Gemological Society
Diamond Certifications from AGS are often used for Ideal Cuts, and describe all the details of the cut to verify perfect proportions. If you want a perfect cut above anything else, you should insist on an AGS cert.
EGL: European Gemological Laboratories
Several related labs around the world operate under this network. You may also see "EGL-USA," which is the US version. They are gaining back their reputation one diamond at a time.
AGL: American Gemological Laboratory
This lab is best known for its work in the colored stone industry, working to provide expert assessments of gemstone identification, treatments, and enhancements. These diamond certifications have recently gained a reputation as consistent and conservative.
IGI: International Gemological Institute
This lab is now working hard to improve its reputation and grading standards, but it will take some time to convince us that the bugs are worked out.AGS: A fairly new lab, AGS specializes on cut grades on fancy shapes.
Other Labs like Global Gemological Laboratory (GGL)
Sure, it is possible that some other labs might be highly qualified and offer excellent information. However, other labs do not enjoy the same reputation and popularity as GIA, AGS, or EGL and will not command as much value if you ever need to sell the diamond. In the most common scenario, other labs will not grade the diamond properly and you are not receiving the actual quality of diamond you want. In most cases, you will end up paying too much for a diamond of lesser quality, so be careful.
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