What is Fluorescence in GIA Diamonds?

Diamond fluorescence - what is it?

Fluorescence in diamonds refers to the emission of visible light when a diamond is exposed to ultraviolet (UV) light. This phenomenon is commonly assessed and graded by the Gemological Institute of America (GIA) as part of the diamond grading process.

GIA grades diamond fluorescence on a scale ranging from "None" to "Very Strong." The fluorescence grade is determined by the strength or intensity of the fluorescence observed under UV light. The presence and intensity of fluorescence can affect the diamond's appearance and value.

Fluorescence in GIA diamonds is simply the visible light that a diamond emits when exposed to UV rays.

In the grading labs they place every diamond under a UV lamp, and the intensity of the light that shows through determines the level of fluorescence given to a diamond on a GIA grading report. Easy! 

So, is fluorescence common? YES! 25% to 35% of all diamonds graded by the GIA in the last ten years had some level of fluorescence (but only 10% of those had a ‘medium’ or higher level of fluorescence). 

Is diamond fluorescence good or bad?

Whether or not you are OK with fluorescence is completely up to you - some people love it, some people don’t. The truth is that most people won’t be able to tell one way or another if a stone has fluorescence unless it is ‘very strong’ (and even then, not always). 

The bottom line is that fluorescence won’t compromise the structure of the diamond in any way, and will have scarcely any impact on the aesthetics of the stone either.

Read more on fluorescence

So, do you think that you are an expert on fluorescence now? Well we’ve barely scratched the surface, so go read more on diamond fluorescence

Dr. Rian Mulcahy
Dr. Rian Mulcahy
Rian is officially a Diamond PhD - just ping us if you’d like to read her fascinating 200-page thesis, titled Facets of Value: An Investigation into the Formation of Worth in the Diamond Market. She has consulted various firms all along the pipeline, from the rough diamond market to the recycled diamond industry. She holds an MA in Globalisation and Development from University College Cork and a PhD in the Sociology of Diamond Valuation from the London School of Economics.