Diamond Fluorescence: What It Means

What is diamond fluorescence?

Diamond fluorescence is a natural characteristic that causes some natural diamonds to emit a soft glow when exposed to ultraviolet (UV) light.

Around 35% of diamonds display some level of fluorescence. In most cases, the glow appears blue, although on rare occasions it may appear green, yellow or orange.

Fluorescence is caused by trace elements, often nitrogen, present within the diamond’s crystal structure during its formation.

Under normal lighting conditions fluorescence is usually not visible to the naked eye, and it does not affect the structural integrity of the diamond in any way.

Does fluorescence affect a diamond’s appearance?

For the majority of diamonds, fluorescence has little to no visible effect in everyday lighting conditions.

Some people actually prefer diamonds with fluorescence because the effect can subtly enhance the appearance of certain diamonds. In some cases, fluorescence can also result in slightly lower prices compared with diamonds that show no fluorescence.

Fluorescence is simply another natural characteristic recorded on a diamond’s grading report.

The diamond fluorescence scale

Fluorescence is graded on a scale that typically ranges from None to Very Strong.

These grades describe the strength of the glow that appears when a diamond is exposed to ultraviolet light.

None

Diamonds graded None do not display any fluorescence when exposed to UV light.

Diamonds without fluorescence are often considered the most traditional choice and may sometimes command slightly higher prices.

Faint or Slight

Diamonds with Faint fluorescence display a very subtle glow when exposed to ultraviolet light.

This effect is usually minimal and difficult to notice.

Medium

Diamonds graded Medium show a noticeable but moderate level of fluorescence under UV light.

In many cases, medium fluorescence offers excellent value because these diamonds may be priced slightly lower despite appearing the same as non-fluorescent diamonds in normal lighting.

Medium fluorescence can sometimes improve the appearance of diamonds with lower colour grades by subtly reducing the visibility of yellow tones.

Strong or Very Strong

Diamonds graded Strong or Very Strong display a more pronounced glow when exposed to ultraviolet light.

In some cases, fluorescence at these levels can slightly enhance diamonds with lower colour grades. However, in a very small number of diamonds, very strong fluorescence may cause a slightly hazy appearance.

Studies from the Gemological Institute of America suggest this occurs in less than 0.2% of fluorescent diamonds.

Is diamond fluorescence a problem?

Diamond fluorescence is often misunderstood. In most diamonds it has no negative impact on appearance or durability.

Many diamonds with fluorescence still display excellent brilliance and sparkle, and the presence of fluorescence does not prevent a diamond from being used in beautiful jewellery.

Because of this, diamonds with any level of fluorescence can still be an excellent choice depending on personal preference.