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What is the Diamond Grading Process?

Why are diamonds assigned grades?

Any high-quality diamond should have a certificate from an accredited laboratory. Do not purchase a diamond if it does not have a certification from the GIA or AGS. It is important to have a certification because it guarantees, without bias, that the value appraised to the diamond by the jeweler or seller is fair and accurate according to the 4 C’s of cut, carat, color, and clarity.

Most jewelers follow the GIA grading system, although some follow AGS. Either way, they are both accurate and just have different names for the same measurements.

The Laboratory Process

Diamonds are submitted to the laboratory by the diamond's current owner. While at the facility, the diamond may not include any symbols or information that would signify the owner, allowing an unbiased grading system. The diamond is assigned a special number and moved to the next step.

First, starting from the outside, gemologists weigh the diamond for carat weight and take measurements. A scanning device takes measurements of size, proportion, and facets. The diamond is weighed on an electronic balance. At this step it is also confirmed that the diamond is natural, synthetic, or a simulant.

Multiple assessments from different gemologists are taken regarding the accuracy of the measurements above as well as the clarity, presence of treatments, polish, symmetry, culet, and girdle thickness. Here, the gemologists also map out the diamond’s interior and exterior inclusions, indicating what the flaws look like and where they are located. If the reports from different gemologists do not agree on a conclusion for every grade, a senior gemologist is brought in to analyze the results and give a final grade.

The lab has a master set of diamonds to compare color and assign a grade. The diamond is compared down the line of increasingly colored gems and tested for fluorescence. Again, the diamond is assessed by several gemologists.

The cut grade is assigned last. The factors of the cut are brightness, scintillation, and fire (all factors of sparkle). If the owner of the diamond desires, or if a dossier certificate is being assigned, the diamond can be laser inscribed with the certificate number by the laboratory.

The certificate is issued and printed with micro-print lines, a hologram, and other security measures. It is then laminated, and sent with the diamond back to the owner.

At The Jeweler

Again, it is extremely important to have a certificate with your diamond. You can send in the diamond yourself to be graded. When purchasing a diamond, ask to see it under magnification and compare what you see to the certificate.

When the jeweler writes the appraisal, the certificate information is taken into account.

Have more questions? Contact us and find out more about the diamonds we sell. With over thirty years in the jewelry business, we’ve seen thousands of diamonds and would love to help you understand your certificate more thoroughly.

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