GIA News

GIA Sheds Light on Fluorescence

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In an effort to help educate the public about the common, but little understood, phenomenon of ultraviolet fluorescence in diamonds, the Gemological Institute of America (GIA) will include, effective immediately, additional information describing fluorescence and its properties in every GIA Diamond Grading Report and Diamond Dossier that carries a diamond fluorescence description of medium or stronger.

A separate, four-color insert addresses the most frequently asked questions about fluorescence, explains its properties in easy-to-understand terms, and includes comparison images of diamonds in both natural and UV light to illustrate varying intensities of fluorescence.  

Some diamonds show fluorescence and some dont, said Thomas M. Moses, GIAs senior vice president of Laboratory and Research. Fluorescence is the emission of visible light by a diamond when it is stimulated by invisible ultraviolet (UV) rays. It is a common characteristic of diamonds. The diamond simply glows under the UV lights, usually a blue color, which most often stops when the energy source causing it is removed.

For more than 50 years, GIA has indicated the presence of diamond fluorescence on its diamond grading reports, but described it on the report as an identification characteristic only not a grade, Moses said. The five terms GIA uses to classify the intensity of the fluorescence are: None, Faint, Medium, Strong, and Very Strong.

This insert will help the public better understand diamonds in general, which gives them more confidence and knowledge when making a decision about a diamond, he said.

GIA has additional information on fluorescence on its Web site, including a scientific article, A Contribution to Understanding Blue Fluorescence on the Appearance of Diamonds, by Thomas M. Moses, Ilene M. Reinitz, Mary L. Johnson, John M. King and James E. Shigley, which appeared in the Winter 1997 issue of GIAs Gems & Gemology.

For more information about GIA Diamond Grading Reports and fluorescence, please visit

16th July 2009