Understanding Diamond Fluorescence

Have you ever noticed the term “Fluorescence” on a GIA Diamond Grading Report? Did you know that some, but not all, diamonds show effects under ultraviolet light?

For most people who purchase diamonds, fluorescence will be a non-issue, but some might be confused by the term. Below are commonly asked questions, and helpful answers from GIA researchers who have studied fluorescence in depth.

What is diamond fluorescence?

Diamond fluorescence, in its most simple form, is the effect that ultraviolet (UV) light has on a diamond. When you stand under a blue light or ultraviolet light, sometimes you can see your whites get brighter or your teeth appear to glow. This is the same effect the diamond has under the UV rays. Fluorescence is the visible light that a diamond emits when it is exposed to the UV rays.

On a GIA Diamond Grading Report, fluorescence refers to the strength, or intensity, of the diamond’s reaction to long-wave UV, which is an essential component of daylight. The light emitted lasts as long as the diamond is exposed to the ultraviolet source.

Is fluorescence common?

Yes. Of the diamonds submitted to GIA over the past decade, approximately 25% to 35% exhibit some degree of fluorescence. However, only 10% of those show strengths of fluorescence that may affect appearance (i.e., strengths noted on laboratory reports as medium, strong, or very strong).

In more than 95% of the diamonds that exhibit fluorescence, the visible color is blue. As blue is the complementary color to yellow, the most common tinted color in diamonds, blue fluorescence can make yellowish diamonds look white or colorless. In rare instances, the reaction to fluorescence is yellow, white or another color.

What impact does fluorescence have on the appearance of a diamond?

GIA studies show that for the overwhelming majority of diamonds, the strength of fluorescence has no widely noticeable effect on appearance. In the GIA Fluorescence Study, it was found that the average person could not make a distinction between a diamond with fluorescence and a diamond without.

In many instances, observers prefer the appearance of diamonds that have medium to strong fluorescence. In rare cases, some diamonds with extremely strong fluorescence may appear hazy or oily; fewer than 0.2% of the fluorescent diamonds submitted to GIA exhibit this effect

Does fluorescence compromise the structural integrity of the diamond?

No. A diamond that fluoresces has the same integrity as one with no reaction to UV. Submicroscopic substitutions and/or shifts in the diamond structure can cause fluorescence or can prevent it. Nothing in either instance inherently weakens or is bad for the diamond.

Should I buy a diamond that exhibits fluorescence?

The preference to buy a diamond that exhibits fluorescence is a personal one, as a diamond’s appearance must be taken as a whole. Other factors can influence color appearance more strongly than fluorescence, such as how the diamond has been cut, whether the diamond is viewed in natural or artificial light, and even what you’re wearing on any given day.

  • paula ray

    What is chemical in diamond to make it fluorescent?

    • giamktg

      The Paula, Fluorescence is not the cause of a chemical. It has to do with UV radiation causing electrons to move within the diamond’s crystal structure. Not all diamonds fluoresce. Blue is the most common color, but you will also find yellow, orange, white, or red.

      Hope this helps.

      • paula ray

        Thank you. Yes this helps.

        Paula Ray-612-968-3777

      • giamktg

        Hi Paula, GIA studies show that for the overwhelming majority of diamonds, the strength of fluorescence has no widely noticeable effect on appearance. Further the structural integrity of the diamond doesn’t change,

      • Wilma Van Der Giessen Gemphoto

        Nitrogen in the shape of an N3 aggregate cause absorption in the region of 415.nm,stimulating the blue fluorescence

  • zoie

    I recently purchased a diamond that has a spec of the below, so I wonder if the strong blue fluorescence will affect the stone in a bad way? Cut*Signature Ideal Polish:Excellent Color:E Symmetry:Excellent Clarity:VS1 Fluorescence:None (which is supposed to be very blue fluorescence according to GIA report, but error on the website)

    • Joseph

      Hi Zoie,
      I am a wholesaler of diamonds and i can assure you that from experience GIA studies are correct, that it hardly affects the stone and it can have as much brilliance as those without. The milky, hazy and oily looks can also be on stones with zero fluorescence. Enjoy your diamond!

  • Burn

    Is this article available in Chinese?

  • LGoptimus

    Hello.
    I have found an interestting diamond in bluenile, but it has medium fluorescense. The jewellry I was talking to thinks that fluorescense can make the diamond to look “milky”. Do you think this is true?
    Regards
    Jonathan

    • Hi Jonathan,

      GIA’s research shows that a diamond with Faint or Medium fluorescence should not have an effect on the diamond’s appearance. When the fluorescence is Strong or Very Strong you might notice an effect on appearance when viewing the diamond in bright sunshine. A diamond with Very Strong fluorescence may have a hazy or oily appearance because its picking up the UV rays of the sun.

      Whether a diamond exhibits fluorescence or not, we suggest you look at any diamond in person, and under different lighting conditions, to determine whether the diamond is right for you.

  • suen

    Can you please advise what grading standard is used to measure fluorescence? I have an issue with a customer who pulled out her pen UV light and some “Nil fluorescence” stones lit up bright blue. She is of course upset and I am shocked. Please explain as I really need to understand to explain to my customer. What is the benchmark?

    • Thank you for your message. GIA grades diamonds under controlled lighting conditions
      so we cannot evaluate what may have caused effect you describe. Also, GIA does
      not use ‘nil’ in describing fluorescence. If you have questions about a
      specific GIA-graded diamond, please contact GIA customer service with the
      report number: lab service@gia.edu

  • Natalie

    Hi,

    I am purchasing a diamond which has been graded by GIA to have strong fluorescence.

    I am concerned that the fluorescence may show up in daylight.

    Could you please tell me how fluorescence is measured and what characteristics are exhibited at each level?

    Kind regards,

    Natalie

    • Natalie,
      Diamond fluorescence, in its most simple form, is the effect that
      ultraviolet (UV) light has on a diamond. When you stand under a blue
      light or ultraviolet light, sometimes you can see your whites get
      brighter or your teeth appear to glow. This is the same effect the
      diamond has under the UV rays. Fluorescence is the visible light that a
      diamond emits when it is exposed to the UV rays.

      The photo above shows the difference between a diamond with no fluorescence and very strong.

      GIA studies show that for the overwhelming majority of diamonds, the
      strength of fluorescence has no widely noticeable effect on appearance. In many instances, observers prefer the appearance of diamonds that have medium to strong fluorescence.

      Hope this helps.

  • Jon Smith

    Hi,

    What I don’t understand about fluorescence is why there are so many mixed opinions about its affect on a diamond’s appearance. It’s seems like the GIA study is very definitive that fluorescence has little to no affect on a diamonds overall clarity/brilliance. But there are still tons of articles online that warn consumers to avoid it, especially in colorless diamonds. While shopping I’m also noticing a price difference of sometimes 1k-1.5k in some diamonds listed online. This scares me because I feel like if fluorescence truly had no noticeable affect on a diamond, retailers wouldn’t be willing to mark them down so much. So, the whole issue just confuses me and I don’t understand why there isn’t a consensus among dealers/appraisers on this. Any further clarification you could give me about this would be helpful.

    Thanks!

    Jon

    • Hi Jon,

      Deciding whether fluorescence is a negative or positive factor depends on one’s personal preference. Ideally, you will want to look at any diamond prior to purchase. While lab reports have important information, a lab report can’t tell you how pretty the diamond is.

      Hope this helps.
      GIA

      • Joseph

        Hi Jon,

        I have many years experience in this field and totally agree with GIA!

  • Tony

    Hi this is Tony, I saw a diamond round color E and VVS2 , excellent very good very good but the fluorescence is strong. Do u advise me to buy it? They made a discount of 35 per cent on the rappaport

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