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Certified Gemstones

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.

First, 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. On the other hand, an appraisal 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, whereas an identification report is the result of objective measurement.

Gemstone Identification Report

Although many buyers are concerned above all with the value of their gemstone, a dependable identification report is actually more worthwhile. 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 information is essential in order 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 unethical for dealers to issue certificates for gems that they are selling, due to potential conflicts of interest. Secondly, 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 include simple heat treatment, fracture-filling, irradiation and diffusion treatment with various chemicals. Gemologists 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.

  • Erstausgabe: May-21-2010
  • Zuletzt geändert: January-22-2019
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    Nachdruck (Text oder Grafik) ohne die ausdrückliche, schriftliche Zustimmung von GemSelect.com (SETT Company Ltd) ist streng verboten.
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Größe und Gewicht

Gems are always measured in Millimeter (mm)

Dimensions are given as;
length x width x depth,
except for round stones which are;
diameter x depth

Select gems by size, not by weight!
Gem varieties vary in density, so carat weight is not a good indication of size

Note: 1ct = 0.2g

Size Comparison Chart