What are IGI Certified Diamonds? | BNT Diamonds

The IGI certificate explained

11 Oct 21

Diamond certification is the process of examining a diamond and reporting on its characteristics according to standards set by the grading laboratory. If you are investing in a diamond, certification is essential as it enables you to fully understand the quality of the diamond.

There are several major diamond grading organisations commonly associated with loose diamonds and diamond jewellery. The International Gemological Institute (IGI) is one of the most renowned grading laboratories in the world.

In this article, we will discuss everything you need to know about the IGI certificate:

  • About IGI
  • What is an IGI certificate?
  • How does IGI grade diamonds?
  • Why do you need an IGI certificate when buying diamonds?

About IGI

Founded in 1975, IGI is the largest independent gem lab in the world. It is headquartered in the heart of the diamond trade, Antwerp, Belgium, with 18 laboratory locations around the globe.

With 650 gemologists grading finished jewellery, natural diamonds, lab-grown diamonds and gemstones, IGI manages to maintain strict control over diamond standards to position itself as a reliable and committed laboratory in the diamond industry.

What is an IGI certificate?

An IGI certificate is a testament to the diamond’s authenticity. Diamond experts from the lab spend a great deal of time using state-of-the-art technology and conducting comparisons with other diamonds in the same category to accurately assign diamonds an IGI certificate.

An IGI certificate is a seal of quality and is internationally recognised as a sign of trust and confidence in the gemological world. With an IGI-certified diamond, you can be sure that the diamond has undergone rigorous testing to confirm the flawlessness of its qualities.

How does IGI grade diamonds?

IGI, like other diamond laboratories, grades diamonds based primarily on the 4 Cs: colour, clarity, cut and carat.


The colour of a diamond is based on a scale from D (colourless) to Z (yellow) and is determined by comparing the diamond to master stones of a predetermined colour.


There are two types of clarity characteristics: inclusions and blemishes. To grade the clarity of a diamond, experts study the gem using a special scope and a 10x magnification loupe to observe the number and nature of these characteristics, as well as their size and position.

The professionals at IGI then place the diamond on a scale ranging from IF (internally flawless) to I3 (imperfect or heavily included).


Unlike other diamond characteristics, cut is determined by man, not by nature. When assessing the cut, experts take into account the cutting precision, proportions and finishing details, which all play a role in the final appearance of the diamond (i.e., brilliance, dimensions).


The carat of a diamond is determined by its weight. The bigger the diamond, the higher the carat weight (one carat is equal to 200 milligrams). IGI laboratory technicians accurately calculate the diamond’s carat weight by using carefully calibrated instruments.


Why do you need an IGI certificate when buying diamonds?

You do not need to buy IGI-certified diamonds per se — but if you do choose one, you have tangible proof of your diamond’s flawless characteristics.

An IGI certificate (or a certificate from another reputable laboratory) is crucial if you intend to sell your diamond in the future, for example, if you are investing in diamonds. In other words, an IGI certificate instils confidence in both the buyer and the seller, as they know exactly what they are getting for their money.

On the flip side, if you choose to buy a diamond without certification, you risk spending more than the diamond is worth — which can be costly if you ever wish to sell the diamond again.

Remember, a reputable seller will have no problem presenting you with an IGI certificate and explaining the various characteristics of the diamond to you.

Buy certified diamonds from BNT Diamonds

Every polished diamond (above 0.30 Ct) purchased from BNT Diamonds carries its own identity via a unique certificate. This laminate-protected document summarises the diamond’s vital information based on the 4 Cs and describes its characteristics that help determine its value.

BNT Diamonds only works with the most renowned labs in the diamond industry:

If you want to find out more about BNT Diamonds’ certified diamonds, consult our diamond specialists today or call us on +32 3 201 24 90.

Fabienne Rauw
About Fabienne Rauw
BNT Diamonds Antwerp

Fabienne, manager of the German market is able to guide every client with finding the right jewel. She takes care of most of the German orders, but also takes other task on her plate. Thanks to her six years of experience at BNT Diamonds she acquainted well with the product and the marketing around it. Her degree in PR ensures that BNT Diamonds is well presented across all media channels. For anyone looking into a new investment opportunity, Fabienne is the perfect guide in this process. No question will be left unanswered, and she will help you every step of the way.

With this article, BNT Diamonds strives to inform you thoroughly about investing in diamonds. No investment can be guaranteed to be without risk or fully according to your expectations. That is why we recommend to research the risks and aspects of investing in diamond properly to ensure that you make the right choice for your portfolio.