Diamond Learning

What does it mean when a diamond is certified?

Have you come across terms like “diamond certificate” or “diamond report” and wondered what they meant? What is the difference between certified and uncertified diamonds? We answer all your questions regarding diamond certification below, including who certifies diamonds, why certification is important, are lab grown diamonds certified, and whether certified diamonds are more valuable than uncertified diamonds.


1. Why do we need diamond certificates?

The purpose of a diamond certificate is to give you a thorough report of what you’ve purchased. Diamond certificates are sometimes also known as diamond reports.

A diamond certificate or report provides a buyer with information about the diamond’s quality, measurements and other characteristics like the Four Cs  – Cut, Colour, Clarity and Carat Weight.

Furthermore, it confirms the diamond’s authenticity and proves your ownership.

2. Does a diamond certificate offer you more value?

A certificate won’t make your diamond more beautiful or improve its quality. However, it adds value to your purchase in the following ways:

  • A diamond certificate gives you peace of mind when you purchase expensive jewellery because it proves your diamond’s authenticity and attests its characteristics.
  • If you ever wish to sell your diamond jewellery on, a certificate will give potential buyers proof of ownership, authenticity and quality.

3. Why are only some diamonds certified?

Diamond certification must be carried out by a gemmological expert, under laboratory conditions. This is a rigorous, costly and time-consuming process.

For that reason, very small or inexpensive diamonds are usually not sent for certification because this would add a disproportionately large cost to their sale price.

Therefore, it makes sense for jewellers to send only solitaire diamonds or large, more expensive stones to be certified at a laboratory. As a rule of thumb, only diamonds above 0.25 carats in weight are certified.

4. Who issues diamond certificates?

There are many independent gemmological laboratories that offer diamond evaluations. The internationally best-known and respected ones are:

Smaller gem laboratories exist too. Their size does not necessarily make their work any less reliable, they just aren’t as famous as the big international institutions.

It’s also important to bear in mind that diamond laboratories do not all employ exactly the same criteria when studying diamonds. What is most important, therefore, is that their work is thorough and independent.

An IGI diamond certificate

5. How do I know if an uncertified diamond is authentic?

If you buy uncertified diamonds from a totally unknown jeweller, the truth is that you’ll have no guarantee of a diamond’s quality.

If you buy an uncertified diamond from a reputable, well-known retailer, they will not risk their reputation and sell you a diamond that’s not what they say it is. Always check your jeweller belongs to the National Association of Jewellers to be sure you’re dealing with a reliable vendor.

6. Can lab grown diamonds be certified?

Yes, just like natural mined diamonds, lab grown diamond solitaires can be certified to prove their size and quality.

If a diamond is lab grown, this will be indicated on its diamond certificate.

Additionally, because lab diamonds are impossible to tell apart from mined diamonds, they are branded with a microscopic laser mark for total consumer protection and transparency. While you cannot see this mark with your naked eye, jewellers can find it by using a specialist magnifying lens.