The “Big Three” grading laboratories as I like to call them have similar processes for certifying diamonds. This process involves several Graduate Gemologists independently assessing and agreeing on the color, clarity, and carat weight of the diamond. This helps reduce the possibility for human error when determining the final grade for the diamond, although it doesn’t eliminate it. You must consider the indisputable fact that there is no exact science behind diamond grading. I know the grading systems sound official and science like but they’re really aren’t. Ponder this statement for a moment, “No two diamonds are exactly alike.” With that being said, how could two different diamonds which are not exactly alike be graded exactly alike? In reality they can’t be.
The other important fact is that the final quality grades are decisions or opinions not scientific calculations. So if they are opinions and every diamond is graded by different labs and different graders then how could there be any consistency? Truth be known, grading labs have a tough time with that, regardless of which lab you talking about. Let’s say for example, that you send a diamond to GIA for certification and it comes back carat weight – .50ct, clarity-SI2, Color-H. Then, you throw away the certification and send the diamond back for a second grading as if it were never graded before. The chance of it coming back SI2, H again is probably 80% and 20% that it’ll come back different. So the grading and certification process is somewhat flawed to begin with. If you can’t get one grading lab to consistently agree with its own grades, how could you expect other labs to agree with another? Again, there’s no easy answer to that question and as an industry we still don’t have it figured out.
From a consumer standpoint the best approach to buying a diamond is to use your best judgment. Read the grading report from whatever lab certified the diamond and examine both the diamond and the certification. Use the certification as a rule of thumb or a starting point, don’t use it as the end all be all. Learn how the grading system works and then compare diamonds side by side under the microscope and decide for yourself which diamond looks better.
GIA, EGL, AGS, GIA – Gemological Institute of America EGL – European Gemological Laboratory AGS – American Gem Society
Recently, GIA seems to have the best reputation for grading diamonds accurately. I challenge this because I’ve seen and compared many diamonds from all three labs and witnessed inaccuracies in GIA grades as often as EGL and AGS. I believe that GIA, EGL, and AGS are the three best solutions for purchasing diamonds however, I don’t feel one is better than the other. One interesting fact is that you’ll pay 15% more (on average) for a diamond certified by GIA because their reputation appears better than other labs. The problem with that is that EGL and AGS are perfectly capable of grading a diamond as accurately as GIA, and usually do. So if that is the case, then why would pay more for a GIA certified diamond that has the same grade as an EGL or AGS diamond? The answer is that you shouldn’t! One of the best deals in the jewelry industry is a diamond certified by EGL; this is because some jewelers assume that EGL isn’t graded as conservatively as a GIA. In the end many jewelers price an EGL certified diamond at less than GIA or AGS stones. This I believe is a mistake because in my experience the grading for all three labs is similar. For a consumer though, purchasing an EGL certified diamond is an excellent opportunity to buy a well graded diamond for much less than you have to. You can learn more about diamond certifications at certified diamonds.
AGS has become very notable for their knowledge about cut and grading a diamond for its potential light performance. Most of what the jewelry industry uses to determine if a diamond is optimized for brilliance is based on AGS’s research. If a jeweler suspects that a diamond is cut very well then he may send the diamond to AGS for certification. If you are looking for a diamond with a very high cut grade you should consider looking at diamonds that have been certified by AGS.
Get more involved in the diamond buying process and understand how the 4C’s work, not just what it stands for. Ask to use a jeweler’s loupe (eye piece) or a microscope to see the diamond under magnification. When looking at the diamond under magnification examine the inclusions for each grade you’re considering then compare them side by side to determine if one looks better than the other. For example, let’s say you are looking at two SI1 diamonds – one is a certified by EGL and the other GIA. After comparing them, you decide that the diamonds look similar but the EGL diamond is 15% less in price. Who cares what lab certified them! Just because some jewelers think that GIA is a better grading lab doesn’t make the diamond certified by GIA better. The grading labs don’t make the diamonds, they simply grade them, a diamond isn’t made better by its certification. A certification is just a piece of paper; you can’t put a piece of paper in a ring and propose. If one diamond looks better than another it probably is, regardless of the grade or what lab assigned it. So in this case the logical choice is to get the better looking diamond, forget about what lab is better and save your money.
Don’t exclude comparing the color. The best way to do this is to ask to see loose un-set diamonds and then compare them side by side. Take a white piece of paper and place the diamonds upside down and next to one another on the paper. The white background adds contrast to the diamond’s color and helps you distinguish the color differences between them. After making a decision on your own about the amount of color a diamond has then refer to the certification to see what the grade is. Again, it doesn’t matter who graded the diamond or what the grade is. In the end you need to see it with your very own eyes and trust your instincts about which diamond is right for you.
Diamond certification is certainly important to have and I don’t think you should purchase a quality diamond without one. I do believe though, that a healthy decision is one that involves you referring to the certification, comparing diamonds side by side, and using your head. Let’s not forget the value of working with a reputable jeweler as well. A good jeweler lends his/her expertise and provides an unbiased opinion about each diamond’s characteristics. The final decision about a diamond and whether it’s right for you – should be made by you. Not a grading lab!