Diamonds and their 4Cs
Discover expertise and laboratories!
A white diamond is always evaluated according to four major criteria, called the 4C: Carat, Color, Clarity and Cut
The weight of a diamond is expressed in carat. In the past, stones were weighed with carob seeds, derived from the Arabic word Qirat. The weight of these seeds was very constant and allowed sufficient precision. Today 1 carat weighs 0.20g. In other words, 1g of diamond is the equivalent of 5 carats (5cts).
The color of a white diamond is evaluated using a scale from D to Z. There are four main groups. Colors D, E and F are white to very white. G, H and I stones have a slight shade of yellow. The J, K and L diamonds have a shade of yellow and the last group, M-Z are considered very nuanced.
The purity of a stone has a strong impact on its brilliance. A very included stone (which contains a lot of defects) will not reflect the light optimally. Attention, the purity only takes into account the defects internal to the stone. Surface defects (scratches, breaks…) are taken into account in the diamond polish.
It is important to assess how the stone was cut. A perfectly cut stone will better reflect the light, the light rays it receives. It will therefore be brighter. For this, we observe three criteria, the polish (traces of polishing can be visible), the proportion of the stone (ratio diameter / weight) and the symmetry of the facets.
When assessing a diamond, one must also take into account the fluorescence, that is to say the reaction to UVs. The best thing is to have no reaction.
These four criteria are “an identity card” of the stone and can be populated on a certificate. Making a certificate has a cost and is not necessary for all stones. It is common for stones less than 1 carat to have no certificate.
On the other hand, the certificate gives a guarantee to the potential buyer of a stone. The beautiful stones have therefore, in general, been certified.
There are multiple gemology laboratories around the world, but not all of them have the same reputation.
The most important and considered international laboratories are the GIA – Gemological Institute of America and the HRD – Hoge Raad voor Diamant (“Diamond Superior Council”). In France, there are several laboratories including the LFG – French Laboratory of Gemology.
The GIA has several laboratories around the world (Bangkok, Hong Kong, New York, London) but is headquartered in Carlsbad, California.
Example of a GIA certificate
The HRD laboratory is located in Antwerp, the world diamond capital.
Example of a HRD certificate
The LFG is based in Paris in the second arrondissement.
Example of a LFG certificate