Diamond Grading – What is the Difference Between Certification Labs?

When shopping for a diamond, the grading report is an important document indicative of what you are buying. A certificate will list the diamond’s properties such as color, clarity, carat size and the cut’s grading, as well as listing any impurities the diamond has. A grading certificate from a dependable gemological lab will also act as security against treated and synthetic diamonds.

Through a series of tests and scientific analysis performed on the diamond during the grading process, it is possible for gemologists to detect the presence of artificial treatments and/or enhancements in color or clarity. A grading report provides a scientific blueprint of the diamond’s properties and characteristics, as well as attesting to the diamond’s authenticity.

Not all grading laboratories are created equal

Each lab uses its own grading system and as a result, a report from one institute may show different results from a report issued by another lab for the same diamond.

Let’s examine the differences between 4 of the most major gemological labs in the world – GIA, AGS, EGL, and IGI.


The Gemological Institute of America, is the leading gemological laboratory in the world. It is the industry’s most trusted and most widely used service. With It’s headquartered in Carlsbad, California, GIA has offices in many cities around the world, employing more than 1400 scientists, educators and certified diamond graders.

Besides gem grading and certification, GIA also provides educational services and carries out intensive research work to keep up with fast changing technologies in the gemological field. GIA is a laboratory that has the highest grading standards and consistency.


Stands for American Gemological Society and is also a US based laboratory (with main offices in Las Vegas). The AGS laboratory is renowned for their scientific approach and research into diamond cut grading. Instead of using an alphabetical rating system, AGS uses a scale of 0-10 for rating a diamond’s characteristics, with 0 as the best and 10 as the worst.

AGS is also known for their ethical standards and consistency in their grading system. In the US market, the AGS lab is the second most widely used lab service after GIA. They are also globally consolidated through offices in Israel, Belgium, India, China and Hong Kong.


Is an abbreviation for European Gemological Laboratory. It is a European founded grading agency and has a big global presence – with offices in London, Paris, Tel Aviv, Tokyo, Johannesburg, among others. EGL is known for pioneering diamond grading techniques for stones weighing less than a carat. They are also notoriously known for the introduction of the ‘SI3’ clarity rating for diamonds and have a large market share in Europe.


Is the International Gemological Institute that is based in Antwerp, Belgium. After GIA, they are the 2nd most well known labs in the world. A significant amount of polished diamonds in the market is graded by IGI and they are very popular in Asian countries.

Recommended Posts