The Difference in Diamond Certificates

Grading accuracy is not always consistent between diamond laboratories. Grading a diamond is a subjective skill. What one laboratory grades a diamond may not be what another laboratory grades the diamond. In fact, gemologists within the same laboratory may not agree on the same grade. At GIA, a small council of gemologists submit their assessments on a particular stone and once there is a gathering of like opinions, the grade is recorded. The grade recorded on the certificate is what determines the diamond’s value. You can expect to pay more for a diamond that has a certificate from GIA versus a diamond that has a certificate from EGL. This is because the grade given at the GIA laboratory is much more strict and is seen as the gold standard within the diamond industry. With a GIA certification, you know exactly what you are getting. Though subjective, the grading process is rigorous at GIA. Other laboratories have a reputation of being anywhere from one to four shades lower than a GIA grade.

Caratcolorclaritycutaverage price


1.00FVS2Very Good$8,357
AGS1.00FVS2Very Good$7,933
EGL Israel1.00FVS2Very Good$4,905
EGL USA1.00FVS2Very Good$6,090
IGI1.00FVS2Very Good$6,602
HRD1.00FVS2Very Good$7,430

GIA (Gemological Institute of America) is extremely strict in assigning color and clarity grades. If a diamond’s quality is on the line of the next higher quality grade, GIA will typically assign the lower grade. GIA uses a computer operated proportion analyzer device (SARIN machine) to determine diamond proportions. The GIA certificate will yield the most money per carat on diamonds, due to the harsh grading scale and global recognition. GIA is the gold standard in certificate grading.

AGS (American Gemological Service) is also very strict in their diamond grading. In fact, some believe AGS is more strict than GIA. AGS is the only laboratory that assigns the cut grade as a numerical value between 0 and 10. 0 is the best cut, while 10 is the least desirable. AGS-graded diamonds will also yield a premium in diamond prices per carat.

EGL (European Gemological Laboratory) is not as strict as GIA or AGS. EGL laboratories differ in consistency throughout the world. The most liberal grading comes from the EGL Laboratory in Israel, while the strictest grading standards are seen in the EGL USA laboratories. EGL-graded diamonds will be available at larger discount than a GIA or AGS-graded diamond. This is because the leniency of the certificate represents anywhere from one color and one clarity grade lower (EGL USA) to up to three color and three clarity grades lower (EGL Israel) in comparison to a GIA or AGS-graded diamond.

IGI (International Gemological Institute) is a reputable diamond grading certificate; however, it is not as strict as GIA or AGS. The IGI certificate is often used to certify smaller diamonds, due to the lower cost of the actual certificate in comparison to other certification laboratories. It is rare that IGI-certified diamonds are more than one color and one clarity lower than a GIA or AGS diamond grade. A deeper discount will be available for an IGI stone in comparison to a GIA or AGS diamond.

HRD is a European-based laboratory that is based in Antwerp, Belgium. The grading laboratory is operated by the Belgian government and is one of the most popular certifications in Europe. The discount will be similar to that of an IGI certificate, as it would be rare that HRD certificate are more than one color and one clarity lower than the GIA or AGS grading.

Often referred to as the fifth “C” in measuring diamond quality, diamond certificates—or certs as they are known in the diamond industry—are an evaluation of a diamond by an independent third party. The diamond certificate shows the results of the evaluation made on a diamond under 10x magnification in color, carat, clarity, and cut.

There are a number of detailed measurements associated with the diamond cut. These measurements are broken down into the following categories: polish, symmetry, table size, crown angles, pavilion angles, and girdle thickness.

The certificate will also specify the diamond’s fluorescence and measurements, and include a diamond plot, which details the placement of the inclusions—if there are any—unique to that particular diamond. This is considered the diamond’s unique identity mark, as no two diamonds are exactly alike.

The information provided by a certificate will provide the buyer with the information necessary to determine the value of the diamond. Without a certificate issued by a reputable agency such as GIA, AGS, or EGL, or HRD, a buyer relies on a jeweler’s integrity that the diamond’s 4C parameters are accurate and not overstated.