Diamond Authentication & Testing

At Sarine Technology Labs, diamond authentication and testing is conducted prior to diamond grading. It is a critical step in the complete and accurate discovery of the diamond's origins.

A detailed look at the diamond under the microscope is the first task performed by the gemologist. The microscope is the main tool to identify clarity treatments, and it allows the expert to identify synthetic diamonds for cases in which inclusions provide enough evidence. It is also effective in identifying most diamond imitations via an examination of the polish quality and possibly inclusion features. Furthermore, by attaching polarizing filters on the microscope, the gemologist can discover more about the diamond type. This is particularly useful to distinguish standard type Ia diamonds from type IIa/IIb/low nitrogen Ia diamonds and to distinguish imitations and HPHT synthetic diamonds from natural diamonds.

After preliminary microscope testing, every diamond tested at Sarine is analyzed by infrared absorption spectroscopy using an FTIR spectrometer. The main objective of this test is to determine the diamond type with precision, and to estimate the nitrogen and/or boron and the hydrogen content of a diamond. This is of great importance in making the decision as to whether a diamond needs further testing for authenticity and/or HPHT treatment.

If a diamond is found to be suspect, then it will be put aside for testing by low temperature photoluminescence spectroscopy. This method is one of the most accurate in successfully and unambiguously identifying synthetic diamonds and HPHT treated diamonds. This technique is executed at Sarine Lab via three different laser excitations, and diamonds are tested at low temperature using a special low temperature immersion technique.

If required, fluorescence information may be collected as an indicator to distinguish natural from HPHT synthetic diamonds. Using standard long wave (365 nm) and short wave (254 nm) UV lamps, most natural diamonds fluoresce stronger under LW than under SW UV and exhibit no phosphorescence when the lamp is shut off. In contrast to this, most HPHT synthetic diamonds fluoresce stronger under SW than under LW UV and exhibit distinct phosphorescence when the SW UV lamp is turned off. Some rare natural diamonds will react similarly, but growth sectors seen under specific UV excitation is distinctly different in such natural diamonds.

More information

For more information about Sarine Lab diamond authentication and testing procedures, please download our Grading Standards Guidebook.

 

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