In the gemstone trade, many gemstones offered for sale are certified to guarantee their authenticity. As a buyer, it is important to understand the different forms of certification, and the types of agencies that provide these certificates.
To start, it is critical to understand the difference between an identification report and an appraisal. A gemstone identification report is issued by a trained gemologist, and summarizes the results of scientific testing of the gemstone. An appraisal, on the other hand, is an attempt to estimate the financial value of the item, and is issued by an appraiser who may or may not be certified. An appraisal is essentially an opinion based on market knowledge, where an identification report is the result of objective measurement.
Though many buyers are concerned above all with the value of their gemstone, a dependable identification report is actually more fundamental. An identification report will state whether your gemstone is natural or synthetic, and whether (in the case of a natural gem) it has been treated in some way. Clearly this knowledge is necessary before one could try to provide a financial appraisal of the gem.
In principle, any trained gemologist could issue an identification report on a gemstone. But in practice, gemstone dealers depend on independent gemological laboratories for certification of their gems. There are several reasons for this. First, it is not ethical for a dealer to issue a certificate for a gem he is selling, due to potential conflicts of interest. Second, modern gem identification requires sophisticated diagnostic equipment that is expensive and complicated to use. The best gemological labs also see many thousands of gems each year, so they have experience that far exceeds that of any individual gemologist.
Detecting gem treatments is the most demanding task faced by gemological labs. Treatments range from simple heat treatment to fracture-filling to irradiation to diffusion treatment with various chemicals. Gemologist use a variety of techniques to detect these treatments, including microscopic examination of gem inclusions, Energy Dispersive X-Ray Fluorescence (EDXF)Spectrometry , Laser Induced Breakdown Spectrometry (LIBS) and Fourier Transform Infrared (FTIR) Spectrometry.