Diamond certificates, otherwise known as ‘grading reports’, are a mostly verifiable record of the stone characteristics in your most valuable pieces of jewelry. Not only do they ensure that the price you purchase the diamond is worth the price tag, they are also essential when trying to sell jewelry or get insurance to protect the piece for a certain amount.

While there are several credible geological labs that can help you catalog and assess your diamond jewelry, we generally recommend diamonds be certified by the GIA or AGS. Here’s an inside look at these two labs and how they assess your valuables.

Diamond Grading is a Subjective Art

First, it’s worth noting that there’s no “mathematical” way to determine a diamond’s color, clarity and cut grade with 100% certainty. Therefore, an inherent degree of subjectivity exists in every grading process. Part of these subjective determinations can be explained by the fact that all labs have varying methods, standards, and experience, despite the fact that they all use the same language developed in the 1950’s by the Gemological Institute of America (GIA).

It is, however, important to do your research to ensure that the lab itself is consistent in its determinations. So even as certificates vary from lab to lab, reporting stricter or looser on things like color and clarity or favoring certain characteristics over others, fortunately these certificate reports are not appraisals, so a small amount of subjectivity is acceptable.

Buy the Stone, Not the Certificate

When it comes time to make a large purchase, no piece of paper, regardless of how appealing it may sound, can make up for an overpriced diamond. If the quality isn’t there, don’t be fooled into thinking you’re getting a steal simply because the certificate indicates special color or clarity characteristics.

In the end, the only way to ensure you’re getting what you pay for is to take a close look at the stone and determine if the price and certificate are in alignment with what you see.

GIA Diamond Certificate

As far as the actual certificates go, reports from the GIA (Gemological Institute of America) have earned it a reputation as the diamond industry’s most consistent lab.

Just make sure the lab of your choice upholds the GIA’s original stance as a “disinterested third party, independent of the buying and selling of the gems”. It is this arm’s length rule that keeps the lab gradings independent of the purchase, sale, or appraisal of diamonds or gemstones.

AGS Diamond Certification

As the “original lab to provide diamond cut grades” as a part of their overall reporting, the AGS (American Gem Society) set the pace for current industry standards which now factor in cut to their certificates. They pioneered the 0 to 9 cut grade scale long before the GIA adopted it as practice, helping determine “0” or “ideal” cut stones.


Very little distinguishes the GIA and AGS from one another. While this makes it difficult to to designate one as a more ‘superior’ geological lab, in our experience, the AGS tends to have slightly looser criteria despite branding itself as the more fancy and refined of the two.

Over the years, industry insiders have come to recognize that this looser criteria often translates into upgraded clarity and color ratings. This makes it appealing for them to seek out an AGS certificate in the event the GIA doesn’t give them the grade they want.

Still, diamonds certified by the AGS generally sell at highly comparable prices to their GIA-grated counterparts.

Ultimately, the best way to ensure you get a fair price on a diamond is to see how much detail you can discern by looking at it closely, perhaps through a loupe or by directly comparing it side by side another stone. Never trust a price tag based on a certificate alone, and don’t hesitate to hire a geologist to give you an experienced, third-party opinion.