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The Diamond : Everything you ever wanted to know about the diamond …

by Julie MIALET 13 Jul 2019

The Stone of April

Diamonds come from far away: the carbon that makes them up must have crystallised for hundreds of millions of years at a depth of more than 200 kilometres, under enormous pressure. It is volcanic eruptions that push the diamonds to the surface. The first of them were discovered 2000 years ago in India, and the world’s largest diamonds come from that country. In the 18th century, Brazil became the main supplier, before handing over to South Africa in 1870. Today, it is Australia that holds the strings: one diamond in four comes from there, and almost all of them are reserved for industry. One often wonders about the authenticity of a diamond. Here are some answers to how to recognize a real diamond.


The composition of a pure diamond


The physical properties of diamond


Diamond is a crystal consisting of a single element: pure carbon. It is the bonds between its atoms that make it a unique gemstone with many qualities. Renowned for its extreme hardness, it obtains a maximum score of 10 on the Mohs scale (a measure of the hardness of minerals). Diamond is therefore the hardest substance there is and nothing can scratch it except another diamond. This is why diamond is not only used in jewellery, but also in industry, as it has the ability to scratch or cut any other material. Only prolonged heat above 600°C can cause the diamond to burn.


What does rough diamond look like?


A rough diamond is the gemstone in its original appearance when it is extracted from the rock. Made up of a crystalline network of carbon atoms, rough diamond usually adopts a geometric shape. The most common shape is the octahedral shape (8 faces), but rough diamond shapes of up to 48 faces can be found.

Its colour in its rough state depends on the impurities present in its crystal structure. The range of colours of rough diamonds is very wide: from light yellow to black, brown, green, pink and blue. Even if it shines only slightly before being cut and polished, the rough diamond already possesses a special light that makes it an incredible gem.


The criteria for recognising a real diamond


The authenticity of a diamond is established according to four main criteria, called the 4 C’s: Carat, Color, Clarity and Cut.

Carat: the weight of the diamond

The weight of a diamond is expressed in carats. In the past, stones were weighed using the seeds of the carob tree, derived from the Arabic word “Qirat”. The weight of these seeds was very constant and allowed sufficient precision.

Today 1 carat weighs 0.20 g. In other words, 1 g of diamond is the equivalent of 5 carats.


Colour: the colour of the diamond


The colour of a white diamond is assessed using a scale from D to Z.

There are four main groups. Colours D, E and F are white to very white. The stones G, H and I have a slight shade of yellow. Diamonds J, K and L have a more pronounced shade of yellow and those in the last group, M-Z, are considered to be highly nuanced.


Clarity: the purity of the diamond

The purity of a stone has a strong impact on its brilliance. A stone that is highly included (which contains many defects and impurities) will not reflect light optimally.

Be careful, purity only takes into account internal defects in the stone. Surface defects (scratches, scrapes, breaks) are taken into account when assessing the polish of the diamond.


Cut: the size of the diamond

It is important to assess how the stone was cut. A perfectly cut stone will better reflect the light, the rays of light it receives and will therefore be brighter.

For this, three criteria are observed:

– the polish: traces of polishing may be visible;

– the proportion of the stone: diameter/weight ratio ;

– the symmetry of the facets.

When appraising a diamond, the fluorescence, i.e. the reaction to UV light, must also be taken into account. It is best to have no reaction at all.


Evaluating the price of a real diamond

The certificate of authenticity

The 4 C’s are an “identity card” for the stone and can be found on a certificate issued after an expertise by a gemmology laboratory. There are many gemmological laboratories in the world, but they do not all have the same reputation. The most important international laboratories considered to be the most serious are :

  •  GIA – Gemological Institute of America ;



GIA’s certificate sample

  • HRD – Hoge Raad voor Diamant (« Superior Diamond Council ») ;


  • HRD’s certificate sample


  •  LFG – Laboratoire Français de Gemmologie.
  • LFG’s certificate sample


    Making a certificate has a cost and is not necessary for all stones. In general, gemstones less than 1 carat do not have a certificate. However, the certificate gives a guarantee to the potential buyer of a stone. Beautiful stones have therefore, in general, been certified.


    The price of a 1 carat diamond

    For an engagement ring, 1 carat is the average diamond size used. There is no fixed price for a 1 carat diamond and its price can vary from €2,000 to €25,000. Indeed, the weight of the diamond alone is not the only determining factor. The purity of the stone, its colour and the shape of its cut must also be taken into account. This is what explains the great differences in price. To give you a general idea, we can say that a good quality diamond for an engagement ring costs around €6,000.

    Of course, this is an average price and, once again, the value of a diamond is very variable, as it is subject to numerous and precise criteria. To make you dream (or cry), know that the most expensive diamonds in the world, such as the Hope or the Cullinan are worth several hundred million euros.

    Even if you are not the happy owner of such a jewel, you will have understood the importance of the expertise of a diamond to determine its value.

    If you are interested in diamond’s jewels, don’t hesitate to discover what les Pierres de Julie have to offer in the store…

    We are also available for any free expertise of your diamond jewelry, for that you can send an email with your photos to

    Whether you're interested in buying a piece of jewellery or a stone, a free jewelry appraisal or jewelry resale, Pierres de Julie welcomes you to its Parisian boutique in the Village Suisse, a stone's throw from the Ecole Militaire and the Esplanade des Invalides.

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