Updated January 30, 2017

Diamond Fluorescence: What You Need to Know Before You Buy

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What is diamond fluorescence and is it bad? This is a topic with widely differing views. Learn how it impacts pricing and when it may actually be good.

Finding the perfect diamond for your engagement ring takes a lot of work and learning new terminology.

So you've learned the 4C's and understand how they affect pricing. As if you didn't have enough to worry about, there is one other little thing to be aware of.

And that is fluorescence.

Fluorescence is one of the most misunderstood characteristics of diamonds. Is it bad and to be avoided? Or does it not really matter? And why do some people want fluorescence??

We're here to shine some light (oh, we love our puns) on this subject. We'll go over what it is, when to avoid it, and why you may want it.

What Is Fluorescence in Diamonds?

Fluorescence is when a diamond shows a soft glow under ultraviolet (UV) light. This is caused by certain minerals in the diamond. This effect is totally natural, appearing in a third of all diamonds.

Most diamonds with fluorescence will glow blue. Less than 5% of diamonds with fluorescence will glow yellow, green, orange, or white.

Gemologists determine fluorescence by viewing the diamond upside-down under UV light. Fluorescence has the following ratings:

  • None: Diamond has no glow at all under UV light
  • Faint: Diamond has a very light blue glow under UV light
  • Medium: A blue glow is easily seen under UV light; medium fluorescence can help make a diamond with a slight yellow tint appear whiter
  • Strong - very strong: A deep blue glow is very clearly seen under UV light; usually, a strong fluorescence can make a diamond appear hazy or milky

UV light is like one of those black lights you used to have in the 80's. You know... the ones that make your teeth hilariously white. And of course, the sun also gives off UV light. So in some cases, diamonds with very strong fluorescence will appear blue-ish in sunlight too.

Fun fact: It used to be that colorless diamonds with strong blue fluorescence (with no negative effect on appearance) were very desirable. This was called "blue white" and they were sold at a premium. It was thought that the blue fluorescence made an icy-white diamond even whiter and more beautiful.

However, too many diamond retailers started using this term to sell their low-quality diamonds. This led to the Federal Trade Commission banning the term in 1938. Since then, diamonds with blue fluorescence were thought to be generally bad.

So Is Fluorescence Bad?

Nowadays, fluorescence in diamonds is generally seen as undesirable. But this is not necessarily true. Sometimes, fluorescence can even improve the appearance of a diamond!

So how do you know when it's bad and when it's good?

Here are some general observations you should be aware of:

  • Fluorescence tend to have a greater negative effect on colorless diamonds (D, E, and F). Often, colorless diamonds with strong - very strong fluorescence will appear hazy. This means the diamond looks cloudy and less transparent.

    Screenshot from James Allen Website

    In the above example, the diamond on the left has a strong fluorescence. I've placed a diamond with no fluorescence next to it for comparison's sake. But keep in mind that this level of haziness is a rare case. I had to search for quite a while on James Allen to find this example.

    But in general, if a diamond is graded higher in color (G or above), a strong fluorescence will cause some haziness. It could be just a very slight haziness. But often, even a casual observer can see the difference when compared to a diamond with no fluorescence.

    Tip: What about medium fluorescence on diamonds with high color grades? Usually, it has no effect. However, in rare cases, they could have a bit of cloudiness too. It's best if you can see the diamond in person and compare to other stones.

    But to be on the safe side, you may want to stay away from diamonds with medium-very strong fluorescence if the diamond is G or above.

  • But fluorescence is good sometimes! It improves the color of diamonds with lower color grades (I and below). For below H, a medium to strong blue fluorescence can help make it look whiter. Diamonds below H have a faint yellow tint, and the blue counteracts that. Usually, a diamond can look one whole color grade higher.

    This is great because it means you can save some money. You can buy a diamond lower in color grade, while having it appear whiter.

    Usually, a strong fluorescence doesn't cause as much haziness in diamonds H or lower. But it's still a possibility. So it's still best if you can inspect the diamond in person.

  • Faint fluorescence usually has no effect at all. It will have no haziness in diamonds graded high in color. And it will also not improve the color in diamonds with lower color grades.

Fluorescence and Pricing

Here's the good part! Since fluorescence is generally thought of as a bad thing, diamonds with this quality are often sold at a reduced price.

Here's how it usually works:

  • Diamonds with faint fluorescence are priced the same (no discount).
  • Diamonds with medium fluorescence have a slight discount (2-7%) if the color is H or above.
  • Diamonds with strong - very strong fluorescence have a bigger discount (3-15%) if the color is H or above.

Tip: If you can find a diamond with strong fluorescence that has no noticeable effect on the appearance, that's some great savings. If you're buying online and not sure, a retailer like James Allen will have professional gemologists who can help you evaluate the diamonds.

But remember - fluorescence can improve the color of diamonds with lower color grades. So in these cases, that's factored into the price. In diamonds with color I or below, a medium fluorescence can even increase the price a bit by 2-3%.

Save Money by Buying a Diamond with Fluorescence

The main reason to consider a diamond with fluorescence is the attractive savings potential. You can save a bundle if you're smart and know what to look for.

Diamonds lower in color cost a lot less. And if you get one with medium - strong fluorescence, it can appear whiter without the higher price.

For example:

  • A 1-carat, H, VS2 round diamond with an excellent cut costs around $5,500 - $6,000.
  • With all other characteristics the same, a diamond with the color I and strong fluorescence cost around $5,000. But it can look as white as an H diamond.

However, you will need to make sure the fluorescence does not cause haziness. If you're buying online and can't examine the diamond in person, make sure the retailer is trustworthy and will give you an honest opinion.

Where to Buy Diamonds with Fluorescence

Brian Gavin is one of our favorite online retailers. It specializes in high quality super ideal cut diamonds. And another unique thing about this retailer is that it offers several product lines. One of which is "Brian Gavin Blue". This line offers diamonds with medium - strong fluorescence.

Each diamond in the Blue line has been inspected by Brian Gavin himself to ensure that the fluorescence has no negative effect. Each diamond is still super ideal cut with top quality light performance.

In other words, these are among the highest quality diamonds with fluorescence you'll find.

Brian Gavin offers his Blue diamonds at a great discount - as much as 15%. Below is an example of the price difference. Both diamonds are around the same size, have color of H, and clarity of SI1 (both viewed to be eye-clean). The diamond on the right costs more than $1,000 more than the Blue diamond on the left.

Screenshot from www.briangavindiamonds.com

Keep in mind: because of the high craftsmanship of Brian Gavin diamonds, their diamonds are usually priced higher than other online retailers. But you are paying for diamonds with superior light performance. And the Blue diamonds are guaranteed to have no negative effects.

Bottom Line

To re-cap, here are some of the most important points:

  • Fluorescence causes the most negative impact in diamonds with high color grades (G or above). A strong fluorescence can result in haziness.
  • Medium to strong fluorescence improves the color of diamonds with lower color grades (H or below).
  • Diamonds with medium - strong fluorescence are usually sold at a reduced price. However, if it improves the color of the diamond, it may then have a small markup.
  • Faint fluorescence has no effect at all, on appearance or price.

Really, how you view fluorescence depends on your personal taste. There is nothing wrong with having fluorescence, just as long as the diamond does not appear hazy. Personally, I think fluorescence makes a diamond more unique. And a slight blue glow can be very pretty. It's also a GREAT way to improve the color of a diamond without the extra cost.

    James Allen

    James Allen: Search for Diamonds

    Shop for diamonds at James Allen, a CreditDonkey #1 recommended partner for the best online experience.

Disclaimer: Opinions expressed here are those of the author's alone. Please support CreditDonkey on our mission to help you make savvy financial decisions. Our free online service is made possible through financial relationships with some of the products and services mentioned on this site. We may receive compensation if you shop through links in our content.

More from CreditDonkey:

Diamond Prices

How to Buy an Engagement Ring

How to Buy an Engagement Ring

Best Place to Buy Engagement Ring Online

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