Estimating the quality and true value of diamonds

If you own one or more diamonds, and would like to know their value, our state-approved experts and auctioneers will be happy to offer you their appraisal services.

Our specialists will carry out a free appraisal of your work, and provide you with a precise estimate of its current market value.

Then, if you want to sell your work, we'll point you in the right direction to get the best possible price for it.  

Diamonds are one of today's most sought-after collector's items. If you own one or more, they may be worth more than you think. On the art market, prices for these objects can be very high at the auctioneer's gavel.  

They are particularly prized, and the price at which they sell on the art market ranges from €400 to €71.2 million, a fairly substantial range, but one that speaks volumes about the value that can be attributed to these objects.  

Their appraisal is also very complicated and subject to many rules. The value of your diamond can vary according to many factors, and for all the reasons listed below, it needs to be entrusted to a specialist. 

In 2016, the Oppenheimer Blue was acquired for €53.6 million. Other masterful records were recently set by Winston Legacy, a colorless 163.41-carat pure diamond sold for €44 million.

In April 2022, the 15.1-carat De Beers Cullinan Blue sold for €55.5 million. Discovered in South Africa's Cullinan mine, it is one of the world's most famous diamonds.

The Pink Star, meanwhile, fetched the record sum of $71.2 million, and was therefore sold for over a million per carat.

Order of value from a single diamond to the most prestigious

Main characteristics to take into account when valuing a diamond

To correctly value a diamond, you first need to consider carats (the unit of measurement for diamond weight). One carat corresponds to 0.2 grams of gemstones and pearls.

It is different from the twenty-fourth of fine gold contained in a quantity of gold, when the term carat is used to indicate the level of purity of the gold.

Naturally, the value of a diamond will vary according to its weight. The higher the carat level, the more expensive the diamond. Carats are the first element taken into account when describing a diamond to establish its value. 

However, other parameters will also come into play, such as its color. The Gemological Institute of America has set up a scale to determine an order of value. The more colorless the diamond, the more expensive it will be.

On the contrary, the more yellow it is, the less valuable it will be. The GIA scale runs from D to Z, with D corresponding to a colorless diamond and Z to a light yellow-brown diamond. 

Subsequently, it was also essential to take an interest in the cutting and slicing of diamonds, sometimes referred to as "cutting". In 1919, Marcel Tolkowsky, a physicist and mathematician, carried out extensive research and succeeded in discovering the ideal proportions of a diamond. 

The size of the diamond is very important, as it affects the reflection of light, making the stone appear larger than it really is.

The ideal proportions of a diamond cut were slightly redefined by the International Diamond Council (IDC) in 1978, to achieve even more refraction than with the Tolkowsky cut.

In addition, symmetry and polishing are absolutely essential to guarantee the harmony of the diamond and the perfect proportions needed to reflect light.

Some diamonds are fluorescent. This means they contain particles that emit a visible glow when exposed to UV light. This is why blue diamonds are often found.  

These submicroscopic effects often lower the diamond's value, as non-fluorescent diamonds are often considered the "purest". This parameter is still debated, as some specialists believe that fluorescence enhances a diamond's color.

Finally, polishing can affect the degree of regularity of a diamond. Carried out in two stages, blocking and polishing, diamond polishing can sometimes be affected by a disymmetry that will impact its value.  

Focus on Bleu de France, a royal diamond  

One of the world's most famous diamonds, Hope, is shrouded in mystery and legend. This deep blue diamond, weighing 45.52 carats, is reputed to have a history marked by misfortune. First mined in India in the 17th century, it was acquired by King Louis XIV in 1668 and cut into a 67.1-carat stone known as "Bleu de France".

During the French Revolution in 1792, the Bleu de France was stolen, along with other French crown jewels. The diamond disappeared for several decades, and it was not until 1812, shortly after the statute of limitations had expired, that it reappeared in London. Although it has been re-cut and reduced to around 45 carats, experts believe that it is the same diamond, having been altered to escape recognition.

Over the years, the Hope Diamond has changed hands several times, and each owner seems to have been struck by an unfortunate fate. Stories of tragic deaths, bankruptcies and ruin have reinforced its reputation as a cursed diamond. However, despite these dark tales, the Hope Diamond is today one of the world's most precious and iconic pieces, on display at the Smithsonian Institution in Washington D.C.

In 2016, this exceptional jewel was valued at over $250 million, well above many other famous gems. If you own a rare or historic diamond, it too may be worth more than you imagine. 

Estimated at over $250 million, the Hope Diamond remains an icon in the world of gemstones. Its deep blue color, due to traces of elements such as boron, and its intriguing story make it an object of continuing fascination, proving that it's not just the beauty or rarity of a gemstone that determines its value, but also the stories it carries within.

Find out more about the diamond valuation process

The technical aspect of diamond appraisal

The appraisal of a diamond is based on well-defined criteria, including those of leading certification laboratories such as the Gemological Institute of America (GIA), the Hoge Raad voor Diamant (HRD) in Belgium, and the International Gemological Institute (IGI).

These institutions provide certificates attesting to your diamond's characteristics, namely the famous 4Cs: Carat (weight), Clarity (purity), Color (color), and Cut (size).

These certificates are essential because they validate the quality and value of a diamond on the international market, and are often indispensable at auctions.

The diamond's provenance is also a crucial factor in its valuation. A diamond certified as being from an ethical source, i.e. free from any involvement in conflicts or in the abusive exploitation of human and environmental resources, will have added value.

Modern technologies, such as blockchain traceability, make it possible to guarantee the provenance of diamonds, boosting the confidence of potential buyers.

The technical evaluation of a diamond also includes an analysis of its proportions, which have a significant impact on its beauty and brilliance.

The ideal proportions for a brilliant cut include several key elements: the table (the upper surface of the diamond), the depth (the distance between the table and the base), the crown (the upper part of the diamond above the girdle), and the breech (the lower part of the diamond).

A well-proportioned table allows optimum reflection of light, creating a sparkle that visually enhances the diamond's size. Depth must be balanced to avoid the diamond appearing too flat or too thick, which would affect its ability to reflect light.

Likewise, a correctly cut crown contributes to the dispersion of light into color spectra, while a well-fitted breech prevents light leakage, thus preserving the diamond's brilliance.

Detecting synthetic or treated diamonds is another essential aspect of our expertise. Advanced technologies, such as infrared spectroscopy and X-ray imaging, enable us to distinguish natural diamonds from imitations or modified stones.

These methods are crucial to guaranteeing the authenticity of the diamond and, consequently, its true value.

Finally, fluorescence, which manifests itself as a visible glow under ultraviolet light, is a controversial factor in diamond valuation. While some consider that it can enhance a diamond's color, others see it as a flaw that diminishes value. Our experts carefully evaluate each parameter to determine the impact of fluorescence on your diamond's market value.

By entrusting your diamond to our specialists, you will benefit from a complete and detailed evaluation, taking into account all technical and aesthetic criteria.

Knowing the value of a diamond

If you happen to own one or more diamonds, don't hesitate to request a free appraisal using the form on our website.

A member of our team of experts and certified auctioneers will contact you promptly to provide you with an estimate of the market value of your work, as well as any relevant information about it.

If you're thinking of selling your work of art, our specialists will also be on hand to help you find alternatives for selling it at the best possible price, taking market trends into account.