- Fluorescence is an optical phenomenon that makes diamonds emit visible light (usually blue) when exposed to ultraviolet light
- Fluorescence can influence a diamond´s price as well as its appearance, that´s why it is stated in every gemological certificate
- Important: In gemology fluorescence is not a quality feature, but rather a characteristic for identification
- In 95% of fluorescenet diamonds the color is blue, however, in rare cases different colors are possible as well
The changes in a diamond´s crystal struture that can both - cause and prevent fluorescence - are in no way disadvantageous for the gem stone (more on this). About 25-35% of all diamonds have a varying degree of fluorescence. The intesity of the emitted visible light is graded accordingly:
|Term on the certificate||Explanation|
|None||The diamond shows no fluorescence|
|Faint||UV light makes the diamond show a slight blueish shade|
|Medium||The diamond emits visible light when exposed to ultraviolet light|
|Strong||The reaction to UV light is clearly visible|
|Very Strong||The diamond glows in an intense blue color when exposed to UV light|
Fluorescence plays an important role in diamonds when speaking about its appearance as well as the price. If you like this special optical phenomenon (only 25-35% of all diamonds have it) and find it fascinating, then you should enjoy the discount on these gem stones. We will help you make the right decision in your specific case and can have our partners examine every diamond beforehand.
If you intend to buy the diamond thinking of it as an investment at the same time, we recommend you follow the market view and pay the premium for non-fluorescent diamonds.
Influence on price
Fluoroscent diamonds are usually sold on a discount in the market. Among high color grades (D-G) the difference in price can be up to 15%. The market considers fluorescence disadvantageous which is expressed in price. One reason could be the fear of the so called "overblues": Diamonds with extremly strong fluorescence that can cause the stone to appear hazy. The most famous example for this is the 127 carat "Portugese Diamond", the largest cut diamond of the Smithsonian Collection.
From a gemological point of view studies of the Gemological Institute of America (GIA) come to a different conclusion regarding fluorescence in diamonds - especially when used in jewelry. According to GIA studies the overwhelming majority of fluorescent diamonds do not show any negative relation or influence on the appearance of the gem stone. On the contrary: In many cases test subjects would welcome the effect of fluorescence - for diamonds that show a little color, the blueish fluorescence actually neutralizes the yellow color shade and makes the gem stone appear brighter. This is proven by the most important results of the GIA study from 1997:
1) The (positive) effect of fluorescence on the appearance of diamonds becomes most obvious at lower color grades I to K. At the same time the (negative) effect of fluorescence on price is most prominent among high color grades.
2) The occurence of "overblues" that account for the negative influence of fluorescence on price is extremely rare. Not more than 0.2% of all fluorescent diamonds that are graded by GIA have the hazy appear. In fact, there are so few diamonds of this kind that GIA could not find enough stones to conduct a separate study on the topic.
Interesting in this discussion is also a historical aspect:
Changes in the crystal structure
i) A group of two nitrogen atoms, the A aggregation, prevents fluorescence
ii) A group of three nitrogen atoms, the N3 center, causes blue fluorescence
iii) A group of four nitrogen atoms, the B aggregation, is neutral
iv) One single nitrogen atom is responsible for yellow fluorescence
v) In addtion there is a range of other possibilities and combinations of the above nitrogen variations, that influence the occurence of fluorescence differently