The IGI VS The GIA & The AGS

You may be well versed in the Four C’s of diamond buying (cut, color, carat and clarity), but diamond certification is just as important. Understanding certification is a vital step in buying a beautiful diamond for the right price. A diamond certificate provides a determination of whether a stone is a natural mined diamond, or one that is lab grown and/or artificially treated in some way. Detailed information allows you to know exactly what you are buying. This may seem simple enough, but there are significant variances between diamond laboratories, with some proving more reliable in certain areas than others.

One diamond lab which has entered the conversation more and more today is the IGI (International Gemological Institute). In this article, we will compare IGI to two of the leading diamond labs, the GIA and the AGS, and illuminate the differences between these top tier laboratories.

A certified diamond is analysed by specially trained experts in a specially equipped laboratory where it is put through a series of tests; these tests will ultimately identify and determine the quality grades of the diamond. A trusted diamond certification will come from a third party – an independent company not involved in buying or selling diamonds and presumably with no incentive to understate or overstate its quality. The sole purpose is to provide an accurate analysis of the diamond and its properties. The gemological findings will be listed on the diamond certificate, usually with illustrations that show the proportions of the diamond and the location of any inclusions or blemishes. It is a scientific report that also attests to the diamond’s authenticity and quality.

Accuracy and consistency are key components in a diamond certificate so finding a lab which can deliver reliable results is essential.

Since it was founded in 1931, The Gemological Institute of America has been widely regarded as the most trusted gem lab in the world. They literally invented the diamond grading system that is used by most other serious gemological laboratories today. The GIA is headquartered in California but they have laboratories and schools of gemology across the globe. They are known for their strict grading standards and advanced analytics which ensure consistency throughout their process. Furthermore, they have education and research centers which are dedicated to continuing research within the field. Their color grades run from D-Z, clarity from FL-I3, and their cut grades (for round brilliants) run from Excellent to Poor.

The American Gem Society (AGS) was established in 1934 (a sister organization to the GIA) and features another US based gemological laboratory. While the GIA is known for creating the four C’s, the AGS Laboratories is best known for their detailed and scientific analysis of diamond cut quality and light performance. Their grading is done on a scale of 0-10 with 0 denoting the highest quality (Ideal) and 10 the lowest. The AGS delivers comparable 4C’s grading consistency to the GIA, but are superior when it comes to cut grading. Their research and focus on the complexities of diamond cut results in a more strict and accurate cut grade. The AGS system uses sophisticated computerized ray-tracing to analyze the light performance of the diamond.

*Important Note: At the end of 2022 GIA acquired the AGSL and its intellectual properties including their world-class cut grading technology. AGS Ideal reports are now available through GIA for qualifying diamonds. The AGS Laboratory has been converted to a cut research center for GIA. Existing AGSL reports continue to be valid and desirable among customers knowledgeable about scientific cut quality.

Both GIA and AGS reports are an accurate and reliable certificate for your diamonds, but when it comes to diamond cut, the AGS is able to provide details that the GIA does not reach. If you are considering ideal or super-ideal cut diamonds, they are likely to carry an AGS certificate, as only this lab has the resources and advanced grading framework in place to truly dig into the details of cut and light performance. As mentioned above, a GIA report can now be ordered with an accompanying AGS Ideal report for diamonds that achieve this higher cut grade standard.

The International Gemological Institute is based in Antwerp, Belgium and has facilities around the world. Although you will find IGI certified diamonds in countries all over the globe, these certifications are more widely relied upon in Asia and Europe. IGI tends to service large volume jewelry chains, and therefore issues thousands of reports on commercial quality, mass market diamonds. As a result IGI tends to offer their service at cheaper rates than either GIA or AGS.  IGI is particularly favored for analysis and grading of laboratory grown diamonds as they have been world leader in this rapidly emerging segment of the diamond industry.

IGI has a big footprint and are involved in a number of activities in addition to grading diamonds. They also have very respected schools training gemmologists, as well as rough diamond grading and CAD jewelry design.

On today’s market it is hard not to notice that IGI Lab Grown diamonds seem to be everywhere.  This fact owes to the extensive global footprint of IGI and the fact that they were an early leader in identification and grading of lab created diamonds.

An IGI lab grown certificate has a distinctive yellow color scheme with “Laboratory Grown Diamond Report” on the cover.  The diamond will also be laser inscribed as a lab diamond and noted on the report.

When reviewing IGI certified lab grown diamonds, look for the growth method – either HPHT or CVD - and any mention of post growth treatments.  The designation “AS GROWN” on the report is a statement that the diamond has not been subject to any post-growth treatments or enhancements.