Fluorescence might be the most misunderstood of the diamond characteristics.

Fluorescence is the white light or glow that a diamond emits when it is exposed to long wave UV rays. Most diamonds exhibit a blue fluorescence.  Many people mistakenly think that a diamond’s fluorescence is a negative, when in reality it very, very rarely affects the appearance of the stone.The fluorescence scale has 5 grades: None, Faint, Medium, Strong, and Very Strong. There are those who believe that all diamonds with fluorescence look milky or oily, but that is just not the case. Between 25-35% of all diamonds have some sort of fluorescence, but very few of those have any affect of the stone.  

When you are shopping for a diamond, don’t be afraid of fluorescence… in some cases it can even be your friend. Since there is a negative misunderstanding of fluorescence, sometimes you can get a great discount on the diamond (so use the glow to your advantage).

I tell all my clients and friends to not fear fluorescence from Faint to Strong. However, once a diamond has very strong fluorescence I would recommend taking a look at it in person…just to make sure it doesn’t look milky.

Insider Tip: If the GIA certificate says the diamond has Very Strong fluorescence take a look at it in the sunlight!

Top (www. image.rakuten.co.jp/kishigum/cabinet/ikou_20090907_001/img 10594175660.jpg?_ex=60x60).
Bottom (www.4csblog.gia.edu/2012/understanding-diamond-fluorescence)