How To Understand a GIA Certificate

When buying diamonds, it is key for our clients to understand the journey our stones have been on and where they have been sourced in order to fully appreciate what they are investing in.

This is where a GIA Diamond Report - which outlines a unique, accurate and unbiased report on each individual stone - can be so useful for jewellers and clients when selecting a diamond.

Launched in 1931, the Gemological Institute of America (GIA) was the first to create the concept of the 4cs for diamonds – carat, colour, clarity and cut, and nearly 90 years later, we are still using GIA grading reports to help us find the perfect stones and ensure our clients make the best choices when it comes to their budgets.

With a GIA Laboratory available to us in Antwerp, our team is regularly working with them on testing our stones. Here is our guide to a GIA certificate and how you can interpret each one when it comes to you buying your diamond…

GIA Unique Report Number – every individual diamond that is assessed by GIA will create a unique report number that is specific to that stone and can be accessed online. In some instances that unique number can be inscribed onto the stone’s girdle itself.

Carat – this is the weight of the stone and a GIA report will state the weight of the diamond to the nearest hundredth of a carat.

Colour – a GIA report will state the colour of the diamond from D (which is colourless) through the alphabet to Z which is a light brown colour – the more colourless (D) the stone, the more expensive it will be.

To ensure each report is accurate, all stones are also tested to ensure they are natural and whether they have undergone any treatments in order to achieve their colour – if they have been treated, there will be an asterix next to their rating (e.g: D*).

Clarity – this part of the GIA report will mark the number, size and position of any inclusions within the diamond (inclusions are slight marks which may not be seen by the naked eye but will be found under a loupe/magnifier). On some GIA reports you will have a diagram which list their size and location. There are 11 different grades in clarity ranging from Flawless (FL) through Very Very Slightly Included (VVS) through to Included (I) – in this instance, a Flawless diamond will have more value then those that are Included.

Cut – the cut and polish of a diamond will also be rated by GIA from Excellent to Poor and will be assessed according to its polish, symmetry, weight ratio, durability, brightness, fire and scintillation.

Country of Origin - With sustainability and ethically-sourced diamonds being a key concern for our customers today, the GIA have also launched a new style of report that includes Country of Origin.

Here the diamonds are matched from the polished gemstone back to the original rough stone in order to confirm the geographical origin. This allows us to trace the stone from its initial home deep in the earth and follow the journey it has been on since then to our design team in Antwerp.

For more information on GIA and how you can have your old and new diamonds assessed, get in touch with our team at or visit

Custom Design Noble Fine Jewellery


Reviews Noble Fine Jewellery


Contact us background.jpg




  • Black Instagram Icon
  • Black Facebook Icon
  • Black Pinterest Icon