How To Tell If A Diamond Is Real With A Flashlight?

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Diamonds are considered the most precious and rarest of gems. They are, therefore, highly-priced and beyond what many people can easily afford. That is why buying a diamond piece is not a daily affair.

It is usually an emotional purchase for a loved one or a special occasion. It is something you have to invest in.

The problem is today, there are a lot of fake diamonds in the market as well, that is being passed off as real. Hence why you are encouraged to take your time and be sure, so you can avoid purchasing a fake diamond.

How To Tell If A Diamond Is Real With A Flashlight

But what happens when you have already bought the diamond and are now suspicious of its authenticity? Luckily there are many ways to verify whether your diamond is real, right from the comfort of your home.

A method that’s been a buzz recently, is the claim that you can verify your diamond’s authenticity using a flashlight. It sounds bizarre, so we understand if you are in doubt.

That is why we are here. In this article, we will verify whether or not this claim is true, by examining the behavior of diamonds under the light.  


Do Real Diamonds Sparkle In The Light?

How To Tell If A Diamond Is Real With A Flashlight

The simple answer is yes. Real diamonds do sparkle when held up against the light. That is why light is used as one way of testing whether or not the diamond is real.

But that doesn’t mean that fake diamonds don’t sparkle in the light too. The difference is in how the diamonds sparkle.


What Do Real Diamonds Look Like Under Light?

How To Tell If A Diamond Is Real With A Flashlight

Like we said, all diamonds, fake or real, will sparkle under the light. What is important is how they sparkle. In other words, how do the diamonds look when held against the light?

This is how you can differentiate between real and fake gems. To begin with, if you compare the sparkle of the diamonds, you will find that the real diamond sparkles with more brilliance than the fake one like glass or quartz.

What’s more, real diamond uniquely reflects light. Inwards the sparkle is gray and white, what is otherwise called brilliance. On the surrounding surface, a real diamond will reflect rainbow colors, otherwise known as fire, onto it.

Fake diamonds on the other hand will exhibit the rainbow colors within the diamond. So as not to get confused, remember sparkling is not the same as reflection. Sparkling refers to the intensity (brilliance) with which the cut of the diamond refracts the light.

How To Tell If A Diamond Is Real With A Flashlight

Reflection on the other hand has to do with the color of light that is refracted. In addition, a real diamond can reflect both white and colored light beautifully. Unlike with fake diamonds, you will be able to tell the difference between reflected white and colored light.

You can also use UV or black light, thanks to what is known as diamond fluorescence. This refers to the effect that UV/blacklight has on the diamond, due to the crystalline structure that allows it to absorb and re-emit the energy as visible light (fluorescence).

Only 30-35% of real diamonds have this characteristic, and even then, it differs in intensity from mild to very strong.

How To Tell If A Diamond Is Real With A Flashlight

The diamonds that do not have this are labeled NONE in the GIA diamond report, so it should be easy to identify them. When exposed to UV light, the real diamond will glow blue, although sometimes you may see a bit of red, green, yellow, or white.

The intensity of the blue glow will also depend on how florescence the diamond is. Diamonds with high amounts of fluorescence are cheaper, mostly because due to it the diamonds are hazy or cloudy and do not sparkle as much. The fluorescence, however, enhances the white color in diamonds.


Do Real Diamonds Shine Without Light?

How To Tell If A Diamond Is Real With A Flashlight

Considering that diamonds are known for their brilliant sparkle, many people assume that real diamonds should always sparkle with or without light. That is why sometimes you may find one or two people who cover up the diamond to see if they will still sparkle.

The truth is, as brilliant as diamonds can be, without light, they are just normal boring stones. But that is not an indication that the diamond is good or bad.

You see, diamonds need light to sparkle. That is the whole basis of their brilliance and why they are cut a certain way. It is so that the diamond can maximize the light by drawing in as much of it as possible and then reflecting it out, making it sparkle like a billion stars in the sky.

The clarity and mounting of the diamond also go a long way in helping. So, without any form of light, diamonds will have nothing to reflect and therefore they will not sparkle or shine.

They can, however, glow in the dark in the presence of UV light, but not all diamonds have fluorescence, so not all may be able to.


Can You Tell If A Diamond Is Real With A Flashlight?

How To Tell If A Diamond Is Real With A Flashlight

Now for the question, that has been bothering you most. You now understand the relation between diamonds and light and the different results to expect.

So, we can easily answer the question of whether or not, a flashlight is a viable tool to prove whether or not a diamond is real. The answer is, yes, you can tell if a diamond is real or not by using a flashlight.

That is because, the flashlight is simply a source of light, that allows you to observe the sparkle and reflection of the diamond. What’s more, you’re likely to have a flashlight handy at any point as opposed to a UV light.


How To Tell If A Diamond Is Real With A Flashlight

So, now that we have established that it is possible to authenticate diamond using a flashlight, let us take you through how that is possible:

How To Tell If A Diamond Is Real With A Flashlight

Step one: Switch on the flashlight

This can be the flashlight on your phone, or a torch if you have one. Sometimes, even your bedside lamp will do the trick, if that is what you have handy. Switch it on and hold it vertically with the light shooting up.


Step two: Observe the sparkle and reflection of the diamond

How To Tell If A Diamond Is Real With A Flashlight

For this, you will need to place the diamond upside down on the lens of the flashlight. Now observe how the light passes through and exits the diamond.

You should be able to notice the brilliance of the diamond and how it separates the light into a rainbow of colors as it exits it. The rainbow of color will be reflected on the surface surrounding the diamond and not in the diamond.


Step 3: Use Cubic zirconia or glass to compare

How To Tell If A Diamond Is Real With A Flashlight

Just to be sure, you can also hold up cubic zirconia or glass to the light and observe how they behave. With the simulated diamond, you will notice that the rainbow color is within the diamond and not reflected outside of it. That is because a fake diamond does not have the refractive ability of a real diamond.

Note: While this method can help easily differentiate the real diamond from the fake, while at home, it is not 100% reliable.

There are stones like Moissanite that can not be differentiated using this method. So, ensure you use other methods as well, as the water test.



There are several ways you can test the authenticity of your diamond at home. Using the flashlight is just one of the many.

We would, however, recommend that you try multiple tests and not just rely on one. Better yet, it is always helpful to get an expert opinion just to be sure. They have the proper equipment and knowledge to give you a more detailed analysis.

In the future, to avoid buying a fake diamond, ensure you do thorough research and that you buy certified stones from reputable dealers who can give you a certificate of authenticity.

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