Phosphorescence in Diamonds: The After Glow

Diamonds are celebrated for their brilliance, fire, and clarity. Yet not all of their visual traits are quite as straightforward. One exceptionally scarce and fascinating visual phenomenon that can appear in certain diamonds is phosphorescence. Visible as an unusual afterglow that emerges from the stone when it is exposed to direct sunlight or UV light. In this article we’ll explain what this is, why it happens and how it affects your diamond. 

What is Phosphorescence in Diamonds?

Phosphorescence is a type of luminescence that appears in select diamonds after being exposed to UV light. The effect is best described as a type of afterglow that continues to emit from the diamond for seconds (or sometimes even minutes) which can appear as a blue, orange, yellow or red glow. Phospherescence is a type of luminescence that occurs when a diamond absorbs light and then continues to emit that light even after the original light source has been removed.

This means after particular diamonds are exposed to strong direct sunlight or a UV light they can produce a visual afterglow.

What causes Phosphorescence in Diamonds?

Phosphorescence is an extremely rare feature compared to fluorescence. The intensity, colour and the length of time the afterglow all vary depending on a few key factors. The crystal lattice of the diamond and its chemical composition can all influence the phosphorescence. 

• Trace elements within the diamond: Boron within the diamond is commonly associated with a blue glow, whereas green or yellow phosphorescent glow is produced by the presence of trace nitrogen within the stone. The concentration of these impurities is responsible for the colour and the intensity of the afterglow.   
  
  

• Type of Diamond: Type IIb lab grown diamonds tend to present more boron impurities, which is responsible for producing the unusual orange colour that is recognised in HPHT lab grown diamonds.
  
  

• Strength and Length of Light Exposure: In order for the stone to produce the afterglow effect, the diamond must first absorb the light to “charge” its phosphorescent glow. Meaning they must be placed under direct sunlight or strong UV light. This reveals their phosphorescent glow which can appear for anywhere from a seconds, to in very rare cases, up to several minutes. 
  
  

• The Crystal Lattice (Internal Structure of the Diamond): The internal structure of the diamond is also responsible for the amount of light that becomes trapped within the diamond and the speed and intensity at which it is released.   

Fluorescence vs. Phosphorescence in Diamonds

Fluorescence is not to be confused with Phosphorescence. Fluorescence is the visible glow a diamond produces during exposure to ultraviolet (UV) light, whereas Phosphorescence refers to the visible glow produced after exposure to ultraviolet (UV) light.

Less than 1% of diamonds exhibit phosphorescence compared to about 25-35% of White diamonds exhibiting fluorescence, where they reveal a fascinating blue hue (and can appear as yellow, green or orange glow) when subject to UV or black lighting conditions. This occurrence is also attributed to the presence of trace elements within the diamond such as boron, nitrogen, and aluminium.

Fluorescence is listed on Diamond Grading certificates as very strong, strong, medium, faint or none whereas Phosphorescence is not measured or tested by gemological diamond labs and remains unlisted via diamond grading.   

How does Phosphorescence Affect a Diamond?

Phosphorescence can be observed with your own eyes and doesn’t require a microscope or any special equipment to be seen. Should a diamond possess this feature it can be viewed after a diamond is placed under strong direct sunlight or after exposure to Black Light (within environments such as an arcade, nightclub or bowling alley) where its afterglow will be revealed. 

It really comes to personal preference whether someone appreciates this colour change and subtle glow. Some find it adds unique character, whilst others prefer their diamond to be forever white and colourless.  

Does Phosphorescence Affect Diamond Value?

If a diamond's phosphorescence produces an orange or yellow afterglow it tends to be viewed as a negative trait (as the most desirable diamonds are those which are the whitest and brightest hues) and the distinction can influence purchase decisions.

In circumstances where phosphorescence is very strong, it may even affect the diamond grading process. If the phosphorescent hues become notable under UV light it can become challenging to assign a diamond within the colourless range and they would be unlikely to receive this grading. The luminescence can cause the stone to be assigned a lower colour grading. 

Buyers should be aware that phosphorescence is not listed on a grading certificate and the afterglow is unlikely to be disclosed. This is why when looking for your diamond it is so important to view in-person to assess how it reacts in real life conditions and whether they exhibit these qualities. At JANAI our diamond specialists can explain these qualities together with you and explore these unique characteristics. Guiding you to find the perfect diamond for your Engagement Ring.   

Conclusion

Phosphorescence is one of the subtle and fascinating properties that make diamonds so extraordinary. It adds a layer of scientific intrigue and beauty and understanding this phenomenon helps buyers make informed choices.

When purchasing your diamond engagement ring in Melbourne always ask to view your diamond under different lighting conditions to reveal the true beauty of the stone. Knowledge about these details ensures your diamond sparkles beautifully and is exactly what you envision. 

Phospherescence and Fluorescence are not diamond flaws but purely identifying characteristics. Always ask your diamond specialist about your diamond and request these details to make sure you select the ideal diamond for your forever ring.