Gemological Labs are NOT All the Same
Definitely not. Most smaller gem labs are extensions of local jewelry stores, created solely for the purpose of raising the image of the store’s inventory. But such labs are hardly unbiased and the certificates are rarely accurate.Even the large labs vary a lot in their reliability, definitions of terms and grades, and in their consistency and conservatism.
Here is the lesson about labs that I wrote in the Beyond the Four C’s tutorial.
To make it simple, if you want an honest assessment of a diamond’s true quality, avoid any lab that is not one of those listed below:
GIA — Gemological Institute of America
The most widely respected laboratory in the world today. Certs from this lab are in such demand that diamonds with a GIA cert are often priced 30-50% higher. This premium is also due to the fact that the diamond is truly the stated quality, since GIA is known for its conservative grading. All labs can make a mistake, but GIA labs have been the most consistent for decades.
AGS — American Gemological Society
This was the only large, nationally respected lab that assigns a grade to the overall cut of a diamond. Now they all give cut grades, using varying criteria for each grade. More on that in my future blog, or the upcoming new website. Certs from AGS are often used for all 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-USA — European Gemological Laboratories
Several related labs around the world operate under this network. Please focus on certs from the EGL-USA network of labs if you want to include EGL certs in your search. EGL certs from other labs around the world are NOT as reliable yet. The grades at the non-USA labs are not as reliable, and that reflects on the value of the diamond. EGL-USA labs are consistent in our opinion.
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. The diamond certs have recently gained a reputation as more consistent and conservative, but not popular or well known yet.
Note About Other Labs
Other labs may be highly qualified and offer excellent information. However, other labs do not enjoy the same reputation and popularity as those listed above, and therefore will not command as much value if you ever need to sell the diamond. In the worst scenario — and a very common one — 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 with certificates from other labs.