What is the Diamond Grading Report - The Complete Guide


What is the Diamond Grading Report - The Complete Guide

Foto di un certificato GIA 

Diamond Grading Reports are documents drawn up by gemologists in the laboratories that grade these precious stones. Each report contains the diamond's characteristics, which include the 4Cs: Carat, Color, Clarity and Cut.

The certificate also includes the proportions and sometimes a chart of all the inclusions within the stone.

Who certifies diamonds?

There are hundreds of laboratories in the world that certify diamonds.

The most important characteristic of a gemological laboratory is impartiality of judgement on the diamonds they certify.

This means that the laboratory must also be completely independent of any commercial interest and therefore not be in any way associated with jewellery companies, retailers, jewellers or wholesalers because it would lose the impartiality of its valuations.

Picture of diamonds ready to be graded

How to get a correct valuation

The valuation of diamonds is a subjective matter since it depends on the different opinions of the gemologists involved.

For this reason, the evaluation of the exact same diamond in two different laboratories can give two different results.

To avoid running into what would be a real problem (even if only for the fact of throwing money into an approximate certificate and having to spend more to have it redone by a recognized and reputable institute), it is essential to contact an independent gemological laboratory with an international reputation in order to certify your diamond correctly.

The guarantee of a gemological institute that is recognized worldwide, in addition to its independence of judgement, is represented by the fact that to evaluate a single stone it makes available the eyes and experience of numerous gemologists at its service, for a consistent evaluation in the name of the highest world standards. More than a science, diamond evaluating is an art, preserved in the expertise of the most talented gemologists.

Which are the best gemological institutes in the world?

Auctentic completely trusts the institutes that represent the most respected gemological laboratories in the world diamond industry: GIA, IGI Antwerp, CISGEM, IGI - Italian Gemological Institute, HRD Antwerp, AGS - American Gem Society, EGL-USA.


Pictures of two diamonds with twezeers

The Gemological Institute of America is based in Carlsbad in the United States and is the oldest and most respected gemological laboratory in the world.

Established in 1931, it is to the GIA that we owe the creation of the 4Cs of diamonds and the diamond grading system that is now used worldwide.

The GIA is a non-profit organisation, recognized by all professionals in the diamond sector as independent and impartial.

The GIA laboratories, employing more than 3000 specialists and gemologists, are located in 13 countries, in the world capitals of precious stones and jewels: Antwerp (Belgium), Tel Aviv (Israel), Surat and Mumbai (India), Bangkok (Thailand), Hong Kong (China), Tokyo (Japan), Gaborone (Botswana), Johannesburg (South Africa), New York and Carlsbad (USA).

The level of expertise of the GIA institute is such that it sets worldwide standards for evaluation practice. The GIA, in addition to evaluating precious stones, trains thousands of gemologists through its programmes around the world and the qualifications awarded by this institute are considered the ultimate.

Pictures of GIA gemstones 

GIA gemologists examine more than 2 million diamonds, gemstones and pearls every year, as well as evaluating some of the world's most famous diamonds, including:

  • Hope, also known as the Blue of France, a stunning deep blue diamond (45.52 carats);
  • the Pink Steinmetz diamond, also known as the Pink Star (59.60 cts);
  • the Taylor-Burton, the famous pear-shape, colourless diamond given to Liz Taylor by Richard Burton (69.42 cts);
  • the Allnatt cushion cut yellow diamond (101.29 cts);
  • the De Beers Millennium Star, 203.04 carats, pear-shape and flawless, colourless, described by former De Beers chairman Harry Oppenheimer as "the most beautiful diamond I have ever seen";
  • the De Beers, Centenary, name chosen by the parent company to celebrate the centenary of the company's founding, a 273.85-carat heart-cut, colourless and flawless diamond;
  • the Incomparable, the largest natural yellow fancy diamond, 407.48 carats.

Do you have a GIA certified diamond?

If you own a GIA certified diamond, you have a very good chance of selling it well in the diamond resale market through a company like Auctentic. We have the utmost confidence in GIA certificates as they are the most accurate in the industry.

Send us the photo of your diamond and the certificate to receive a free accurate initial estimate from Auctentic: info@auctentic.com


Logo of IGI Antwerp 

The International Gemological Institute (IGI) was founded in Antwerp, Belgium, in 1975 and is the oldest gemological laboratory in the city.

With 18 laboratories around the world (Antwerp, New York, Hong Kong, Mumbai, Bangkok, Tokyo, Dubai, Tel Aviv, Toronto, Los Angeles, Kolkata, New Delhi, Thrissur, Jaipur, Surat, Chennai, Ahmedabad and Hyderabad), IGI represents the world's most widespread institute.

Its Gemological Training sector is present in Antwerp, Mumbai, New Delhi, Hyderabad, Surat, Ahmedabad, Chennai, Dubai, Shanghai, Cavalese (TN), Ascoli Piceno, Rome, Marcianise (CE) and Trecastagni (CT) with a wide range of courses for both professionals and gemology lovers.

IGI Antwerp certificate for jewellery identification 

But other records belong to IGI Antwerp:

  • its Gemological Training sector was the first to create training courses on rough diamonds;
  • it introduced the laser marking patent to uniquely mark diamonds;
  • it was the first laboratory to issue identification certificates for jewellery;
  • is the only laboratory in the world to offer diamond repair and recutting services;
  • it was the first laboratory in the world to seal diamonds to provide the guarantee of protection;
  • it created the first complete reference table on diamond cutting.
  • It was the first institute to achieve permanent inscription on the diamond table using ion ray technology;
  • it created the 'Hearts and Arrows' certifications, recognized worldwide, to attest to the perfect symmetry of certain brilliant-cut diamonds (only 1 in 60,000 diamonds deserves this particular certification).
CISGEM - Centre for Information and Gemological Services

The CISGEM Institute was established in 1966 by the Ministry of Industry as the Public Institute for the Quality of Gemological and Precious Materials, and is still a point of reference for the goldsmith sector. It is part of the Italian Gemological Foundation and is one of the seven prestigious laboratories accredited in the LMHC group - Laboratory Manual Harmonisation Committee (together with the Japanese CGL Laboratory, the DSEF German Gem Lab, the GIA, the GIT Gem Testing Laboratories of Bangkok and the Gubelin Gem Lab Ltd of Lucerne), for the certification and drafting of standards for the unification of gem nomenclature.


Founded in 1973 in Milan, it is a non-profit organisation that combines the work of gemological analysis with the dissemination of research and knowledge, carrying out training activities and practical courses. The Milan office houses the analysis laboratory, the study and training centre, while at FOR.AL. in Valenza (Professional Training Consortium of the Alessandria area) and the Italian Goldsmith Academy in Catania it is possible to enrol in specialisation courses organised by the I.G.I.


HRD ANTWERP certificate HRD ANTWERP certificate[/caption]

The HRD - Hoge Raad voor Diamant - stands for the High Council for Diamonds and is an institute founded in 1973 in Antwerp, Belgium. The institute's gemological laboratories are located in Antwerp, Mumbai and Istanbul and are equipped with the most sophisticated technology, used by the best experts in the field. In addition to the laboratories, HRD Antwerp also has representative offices in Dubai, Hong Kong, Madrid, Ramat Gan, Shanghai and Surat.


American Gem Society logo 

The American Gem Society was founded in 1934 by a small group of jewellers with the aim of protecting jewellery buyers. The AGS is renowned for being one of the first laboratories to offer reports on diamonds in sought-after cuts such as princess, emerald and oval. To join the AGS, jewellers, retailers, suppliers and affiliates must meet the highest standards in terms of ethics and work quality, pass an entrance examination and undergo several annual audits.


picture of loose round cut diamonds

EGL USA has been involved in gemological research and laboratory analysis for more than three decades in order to protect both the diamond industry and jewellery buyers.

EGL USA certifies diamonds, gemstones and jewellery characteristics. It has been headquartered in New York, in the heart of the diamond district, since 1977, with an office also in Los Angeles. To date, the two laboratories evaluate diamonds and gemstones exclusively in North America.

Why is it important to have a diamond certified?

In short, the information contained in the certificate (if it is drawn up by a recognised and respected international laboratory) allows the diamond to be identified and easily sold worldwide. The characteristics of the diamond, documented by a reliable source such as the GIA or the IGI of Antwerp, allow specialists to estimate the stone without even having to see it. These types of certificates tell you everything you need to know, from the precision of the cut to the placement of inclusions - all factors that contribute to determining the price of the diamond.

This also applies to the buyer, as it helps to make comparisons with other diamonds on sale, thus allowing the buyer to choose the stone that best meets their needs, including in terms of affordability.

Why does a certificate help to sell a diamond better?

The certificate contains the information necessary to valuate your diamond accurately. We talk about the basic characteristics of the diamond, such as the 4Cs - carat weight, cut, colour and clarity. But most reports and certificates also contain other informations that specialists draw on to analyse the stone's attributes without having to look at it, such as proportions and fluorescence.

In addition, a certificate issued by the GIA (or other recognised laboratory) can really increase the value of your diamond when it comes time to resell it through a service such as Auctentic. As the GIA is synonymous with global standards and the benchmark in diamond evaluation, we place the utmost trust in their certificates as they are the most accurate on the market.

What about other certificates?

Certificates issued by other laboratories with an international reputation can also be an added value . All reports contain some accurate information such as the exact weight of the stone, which can only be calculated when the stone is loose and not yet mounted. Assuming you have a certificate where the quality of the cut is not established, an expert can deduce it if the proportions, table size, symmetry and polish are described instead. And this is no small detail: for example, a diamond with an Excellent cut can increase its value by up to 30%.

Where can I sell my certified diamond?

With a good certificate in hand, among jewellers, auction houses and private individuals, there are many people interested in buying a quality diamond, as it is easily resalable and a safe haven.

Even if in jewellers the waiting time can be long, as in the case of a consignment, it must also be considered that an immediate purchase can often result in a lower profit.

Auction houses take time to catalogue the stone and have very high sales commissions.

Selling it online using a fast and secure service such as Auctentic means not only a considerable saving of time but also a better profit thanks to the system of direct offers that come from an audience of international professional buyers.

Send your certificate and the photo of the diamond to our specialists to receive a free, initial estimate, with no obligation to purchase, at info@auctentic.com

Trends in the diamond market

At Auctentic we help every day collectors and sellers from all over the world to resell high quality diamonds, we know the market and which stones are the most popular in a given period.

In the diamond market, some stones with certain characteristics always hold the market and therefore also the resale market, allowing a faster sale than other types of diamonds. These trends are always evolving but if you have a certified diamond it is clear that you can sell it more easily and get more from the sale, thanks to the competition of international buyers who are part of Auctentic's network of certified professionals.

Learn how to sell diamonds without a certificate