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Why Do Diamonds Turn Blue In Blacklight?

Why Do Diamonds Turn Blue In Blacklight?

Buying a diamond requires some knowledge – especially since the goal is to find the ideal stone. There are so-called identifying characteristics that every diamond buyer should be aware of so that they can make an informed decision.

One of these identifying characteristics is diamond fluorescence. It’s a bluish glow that gems will emit when exposed to ultraviolet rays.

Today, we’ll answer the frequently asked questions about diamond fluorescence, such as: What is diamond fluorescence in the first place? Why do diamonds turn blue in blacklight? Is that good or bad?

Keep scrolling to the very end! We’ll help you find a perfect diamond!

What Is Blacklight?

A blacklight lamp or Wood’s lamp emits long-wave (UV-A) ultraviolet light that is barely visible. It was named after Robert Williams Wood, the scientist who invented Wood’s glass UV filters.

The blacklight lamp blocks most of the light visible to the human eye and emits a dim violet glow when turned on. The catch is in the violet filter material placed in its bulb or in the lamp housing that lets through only UV-A light.

Blacklight lamps are labeled with the letters “BLB,” which stands for “blacklight blue.” 

There’s also a type of this lamp that produces ultraviolet light but has no filter. It’s identified by the industry designation “BL.”

Wondering what some sources of blacklight are? Here’s a quick overview:

  • Specially designed fluorescent lamps
  • Mercury-vapor lamps
  • Light-emitting diodes (LED)
  • Lasers

What Is Blacklight Used For?

Blacklight is necessary when people need UV-A light without visible light. Such light is used for observing fluorescence. On that note, blacklight lamps are commonly utilized for:

  • Medical diagnostics
  • Medical therapy
  • Various lighting effects
  • Detecting fake money
  • Insect lamps
  • Repairing refrigerators and conditioning systems
  • Rock-hunting
  • Identification of fluorescent diamonds

Is Blacklight Dangerous For People?

It can be a potential hazard – especially if your eyes or skin is exposed to it for a long time. The negative effect on the eyes can be both short-term and long-term. 

The World Health Organization has issued a warning that UV-A light is not only responsible for skin aging and wrinkling but increases the risk of skin cancers, too. 

Remember this the next time you enter a tanning bed! 

What Is Diamond Fluorescence? 

Some objects emit visible light. This glow is called fluorescence.

Diamonds can be fluorescent, too. About 95% of these diamonds emit bluish light when you expose them to ultraviolet (UV) rays coming from the sun or fluorescent lamps. Rarely, the emitted light can be yellow, green, red, or orangy. 

And as soon as you remove the source of UV light, the glow stops. 

Will All Diamonds Show Fluoresce?

No, not all diamonds display fluoresce. Only around 25% to 35% of these precious stones will show a degree of fluorescence.

Related Read: Do Fake Diamonds Glow Under Ultraviolet (UV) Light?

Is Fluorescence A Grading Factor For Diamonds?

As we have said, fluorescence is an identifying characteristic of diamonds. GIA confirms that – but does not define fluorescence as a grading factor such as the 4Cs (color, clarity, cut, and carat weight). 

GIA classifies a diamond’s fluorescence by its intensity – and there are five levels of it:

  • None
  • Faint
  • Medium
  • Strong 
  • Very Strong

The color of the glow is noted only when the fluorescence is Medium, Strong, or Very Strong. When the glow is assessed as Strong or Very Strong, a diamond can appear blurry or cloudy under direct sunlight.

During the grading procedure, gemological labs such as GIA or AGS evaluate the diamond’s fluorescence intensity, too. You can learn more about the diamond color and fluorescence from the GIA Diamond Grading Reports.

What Triggers Fluorescence?

When it comes to natural diamonds, the main cause of fluorescence is the presence of certain chemical impurities in their composition. These impurities trigger the glowing effect in the presence of an ultraviolet light source.

Can Fluorescence Enhance A Diamond’s Appearance?

Some experts think so. They believe this natural phenomenon can make a yellow diamond look whiter. For example, diamonds with I to M color grades appear more colorless under direct sunlight and artificial UV light. 

Therefore, diamonds with a Very Strong, Strong, or Medium fluorescence that are near colorless or faint yellow will cost a bit more per carat than similar diamonds without the fluorescence.

However, it’s the other way around when it comes to diamonds with higher color grades. Namely, diamonds in the D to H color range that have bluish fluorescence are valued less than similar stones without this effect.  

Why? Well, the bluish fluorescence can cause a hazy or oily appearance in the diamonds mentioned above. If it is any consolation, this happens only when the fluorescence intensity is very strong – and even then, not in all cases! 

Where To Buy A Fluorescent Diamond?

If you’ve set your mind on buying a fluorescent diamond, the question to ask yourself is: Should you buy it locally or online? Let’s find out!

Buying a diamond online is usually cheaper than turning to a local diamond dealer. It is even more affordable when it comes to fluorescent diamonds. 

On the other hand, it’s not a good idea to purchase diamonds without seeing how they look face up in the direct light. You should check a fluorescent diamond under the blacklight, as well. 

If you buy a strong blue fluorescent diamond online, you might end up with a hazy-looking stone you don’t like as much as you hoped. For this reason, it would be wise to make sure that you have 30-day free returns.

Is Diamond Fluorescence Good Or Bad?

Currently, most diamond experts consider diamond fluorescence as a “defect.” As a result, such diamonds can often be purchased at a sale price. 

Then again, some experts do not agree with such a notion. They believe diamond fluorescence is a good thing. We do not choose sides but rather try to stay objective. So, let’s see what the arguments are on both sides, shall we? 

So, What Are The Negatives Of Buying A Diamond With Fluorescence?

Diamonds featuring Strong or Very Strong fluorescence can sometimes have an undesirable milky appearance. If you want to buy a fluorescent diamond, make sure it is not hazy or cloudy. In the industry,  such stones are called “overblue,” by the way.

The good news is that this problem isn’t that common: It happens to only around 2-3% of colorless diamonds (D, E, F) that feature a Strong or Very Strong fluorescence.

It’s a common misconception that diamond fluorescence affects the gem’s sparkle and beauty negatively. We’d say that’s nowhere near the truth. 

Both sparkle and brilliance are determined by how the stone is cut. Whether or not the diamond has the ability to glow in blacklight has nothing to do with this.

The second common misconception has to do with the connection between the fluorescence and durability of the diamond. Once again, there is no evidence to back up this claim. 

Fluorescence is caused by chemical impurities – and cannot weaken the stone’s hardness or strength. 

How Can Diamond Fluorescence Be A Good Thing?

First of all, there’s the appearance. A lot of people find the glow-in-the-dark effect cool-looking. Most importantly, diamonds with fluorescence are more affordable. They are usually sold at a discounted price ranging from 5%-25%. 

And it is always a good idea to save money – every wise shopper will tell you that!

Here’s the thing: Two diamonds with similar carat weight and color and clarity grades can seem almost identical in every aspect but their cost. The price difference can reach 30%. The only distinction between the two stones is that the cheaper version is fluorescent – and the more expensive one is not. 

Finally, fluorescence can help improve the color appearance of a diamond in the lower color range. As we’ve already explained, blue fluorescence will neutralize the yellowish tint a diamond has and make it appear whiter – by half to one grade higher.

What should you decide? As you can see, there are advantages and disadvantages on both sides. 

At the end of the day, it is up to each person to reach their decision based on the budget, taste, and preferences. Fluorescence is a highly subjective characteristic.

You can go either way, too. It’s perfectly okay to decide to purchase a fluorescent diamond – or let it pass. You should listen to your heart and determine what you like and want. 

Now that you know all the facts, you can make an informed decision – one you will never regret!

Can Fluorescence Be Used To Tell If The Diamond Is Real Or Fake?

If you think so, you probably found some info on the Internet. There’s a lot of misinformation related to fluorescence found online.  

You cannot identify whether a diamond is real or fake based solely on fluorescence. It has never been used for determining a diamond’s authenticity.

Why? We already answered this question earlier. If you remember, only about a third of diamonds fluoresce. Therefore, more than 60% of them don’t. Moreover, numerous other minerals and gemstones have fluorescence, as well. 

There’s absolutely no logic behind using a blacklight to determine whether a diamond is real or not!

Do Lab Diamonds Glow In UV Lights, Too?

Yes, they do. Lab-grown diamonds will glow in different colors in blacklight- just like the natural ones. 

Submicroscopic structures within the diamond crystal during its “growth” cause fluorescence. Once again, blue fluorescence is the most common for lab-made diamonds due to nitrogen atoms aligned in the carbon lattice.

Interestingly, thanks to the alloys, lab diamonds can display rare fluorescent colors, too. That means they can turn orange or yellow under the blacklight – not just blue! 

Related Read:

Best Tips On Fluorescent Diamonds

Fluorescent diamonds are not much different than the regular ones – until you turn on the blacklight lamp, that is.

You decide whether you like fluorescent diamonds or not. It’s all up to your personal taste – they are neither good nor bad!

Fluorescence can sometimes improve the color of the stone.

The color and appearance of a diamond are not necessarily ruined even when strong blue fluorescence is present.

If you don’t mind your diamond glowing in the blacklight, you can save some money – fluorescent diamonds are more affordable.

It is best to find out all about the retailer’s return policy before buying a fluorescent diamond – or any other diamond, for that matter. 

Buy fluorescent diamonds only from reputable sellers so that you don’t get tricked into buying one of poor quality. 

When shopping for a fluorescence diamond, always check how it looks under both normal and UV lighting. It’d be ideal if you could check its appearance in daylight, too. 

Strong Blue Fluorescence in diamonds causes them to appear hazy or milky.

If you plan to buy a fluorescent diamond with a color H or lower, it is best to opt for one with Medium Blue Fluorescence.

See Also: Can Ultraviolet (UV) Light Destroy A Diamond?

Final Words

You now know what fluorescence is and why diamonds turn blue in backlight.  Even though there are polarizing views, the decision of whether or not to buy such a diamond should be only yours. 

Try to take in all the pros and cons – and make an informed decision. Don’t be afraid to ask around when shopping for a diamond, too. Every honest, good jeweler will address your concerns and help you reach a decision.

To recap, fluorescence rarely has any negative impact on diamonds. Still, it makes beautiful diamonds more affordable – and that’s a plus for you.

Read Also: Do Diamonds Emit Light?

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