The primary role of laboratories is to certify that a diamond is of natural origin and to grade its quality. All of this information is laid out in a document (a “certificate”) which is issued with the stone.
Firstly, a certificate constitutes a guarantee that the stone is of natural origin when this is the case. Indeed, if the diamond is natural but has undergone a treatment, this is indicated in the certificate.
Secondly, a certificate grades the quality of the stone by describing its physical characteristics. To do this, four primary criteria are used: the 4 Cs (Carat, Color, Clarity, Cut). So the certificate does not in itself determine the price of a stone, but it does certify its essential attributes and is used to estimate the value of a diamond. As for synthetic diamonds, laboratories have started to deliver diamond certificates for lab-grown stones weighing 0.15 carat and up in 2007. These documents are immediately recognizable because they are of a different color.
Laboratories are scientific organizations and are useful in that sense, because they are reassuring to the consumers. Nevertheless, despite strong scientific bases, the grading of color diamonds remains a recent field, contrary to diamonds, which have been around for hundreds of millions of years.
The following chapters explain the functioning and the methods of laboratories.