Do Fake Diamonds Shine Rainbow? (All You Need To Know)

Do Fake Diamonds Shine Rainbow

Do you know how to spot a fake diamond? There are several ways to spot a fake though sometimes it is quite difficult, especially with mounted stones.

If you are in the market for a diamond, you should definitely learn as much as you can about diamonds–both the 4Cs of real ones and how to spot a fake. 

Diamonds disperse light as it passes into and out of the stone. Light disperses differently depending on the type of material, so an experienced person can tell if a diamond is real based on how it reflects light. Both real and fake diamonds will make rainbows (called fire) due to this prismatic effect. 

Fake diamond makers are tricky and have come close to producing very good diamond simulants that can even produce fire when in white light.

If you see rainbows, your stone still may be fake, but if your stone is very bright and produces a lot of fire, it may be a very well cut real diamond. 

Check out everything you need to know about whether diamonds shine rainbow and ways to spot a fake. 


What Makes Diamond Rainbows?

Diamonds, like other prisms, take white light and bend it so it disperses it into the rainbow of colors.

If you look at a diamond under the white lights of a jeweler, or in bright sunlight, you may see the most rainbow fire.

This is because the diamond’s facets are splintering the white light so you see it as different colors. 

You may see the fire coming out of the sides of the diamond, or reflected as rainbows on other surfaces. 

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Read also >> Are All Diamonds GIA Certified? (All You Need To Know)

Do Fake Diamonds Make Rainbows?

As you know, glass or crystal prisms also shine rainbow, so it is possible for non-diamond substances to create rainbows. For this reason, just seeing fire from a stone does not confirm that it is a real diamond. 

Diamonds do disperse light differently from fake stones, but it will take a lot of practice looking at real and fake diamonds to be able to spot a fake. 

That said, a diamond’s cut will determine how much rainbow fire you see flashing from the stone. Very good or Ideal cuts are made to optimize both the sparkle of the diamond (black and white) and the rainbow of the stone (fire). 

Many diamond imitators are not cut to the exacting specifications of real diamonds, so if you have a stone with excellent fire, and it creates a ton of rainbows all over the place but is still bright, you may have a real stone on your hands.

You should of course take it to a trusted jeweler to confirm. 

What Does Diamond Sparkle Mean?  

Ok so rainbows coming from the diamond are called fire, but what is sparkle? Sparkle doesn’t refer to the rainbow colors that come from the diamond when a light is shined on it, but rather the play of light and dark across the stone.

Sparkle is also determined by cut–a better cut will have much more sparkle than a poor cut. 

Diamonds are also graded on brightness–how much light is reflected from the stone. And they are graded for pattern, which should be uniform and have crisp black and white areas in a symmetrical and uniform pattern. 

Pattern and sparkle together are called “scintillation.”

Do Fake Diamonds Sparkle as Much as Real Diamonds?

Fake diamonds are made to sparkle, which is why they are used in so much costume jewelry and trend jewelry.

There are other substances that jewelers and designers have found that allow wearers to enjoy a little sparkle without forking over the cost of a real diamond. 

So yes, fake diamonds are made to sparkle like a crystal chandelier–obviously not made of diamonds. 

But just like with fire, fake diamonds will not typically be cut to the exacting proportions to make them sparkle exactly like diamonds, because diamonds are so good a dispersing light.

If you really want the most beautiful balance of sparkle and fire, you will have to go with a well-cut real diamond (natural or lab). 

Read also >> How Long Does GIA Certification Take? (Here Is What To Do)

Do Precision Cut Crystals Have Fire and Sparkle?

Some jewelers specialize in jewelry made from a crystal that is cut to exacting standards to optimize its refraction.

One example is Swarovski crystals, which are cut using computer modeling of light refraction so the facets are ideally placed. 

Swarovski also uses a proprietary blend of crystals that creates a very clear crystal–which allows light to pass through it and reflects as sparkle or fire. 

This is one example of well-cut simulated diamonds that have excellent sparkle and shine–though they still don’t behave as a real diamond would. 

How to Spot a Fake Diamond

So just because a stone flashes rainbows all over your wall doesn’t confirm that it is a real diamond (unfortunately).

So how do you know if something is fake? There are a few tests. The only real way to be totally sure is to find a reputable jeweler and take the stone to them. Make sure you choose a jeweler that has experience with diamonds. 

You can also send a diamond to the Gemological Institute of America for grading if you cannot find an independent jeweler that you trust. 

Here are some tests to determine if your diamond is fake (many will have to be performed on a loose stone):

Does it Float?

If you put your loose diamond in water, will it float to the bottom? Diamonds are more dense than imitations, so they will quickly fall to the bottom.

An imitation stone will typically float at the top or just below or drop more slowly (unless they are a very large size). 

Does it Fog?

If you breathe on your stone, does it create fog? A real diamond typically won’t fog up or it will dissipate quickly, but a fake one will fog up just like a mirror. 

Are There Inclusions?

Fake stones don’t have any natural inclusions like little spots or dots formed by impurities that were captured when the stone was formed. If you look at your stone under magnification, can you see any spot in it? If not, it may be fake. 

If you do see some inclusions, it is more likely your stone is real. 

However, some diamonds are naturally flawless, so this isn’t a foolproof test. Lab-grown diamonds are becoming increasingly easy to make flawless, so there may be more of these perfect gems out there and this test might not be determinative. 

Does it Glow?

Some real diamonds have fluorescence, though not all. If your stone glows under a black light, it is probably real. Imitations don’t typically have fluorescence.

Can You See Through It?

Put your stone upside down on a piece of newsprint. Can you read the letters through the stone? Real diamonds refract light so well that you can’t see through them like glass, even though diamonds are technically clear. 

Can It Take the Heat?

This might be the most dangerous option, but if you hold your diamond over a lighter or other fire source (use tweezers that aren’t metal!) and then place it in a glass of cold water, does it crack? A real diamond will be unaffected by the temperature change, but many imitations will crack or shatter. 

Does it Conduct Heat? 

You can get a diamond tester online, which helps you test for thermal conductivity at home (this is one way jewelers test diamonds). 

Should I Do The Diamond Scratch Test?

Yes, diamonds are very hard substances, and will scratch most other substances (like glass and many other gems).

It used to be recommended that you could scratch a mirror with your stone to tell if it is real, though many of today’s imitation diamonds are also hard enough to scratch the glass (though they can’t scratch a real diamond). 

Can I Tell a Lab Diamond?

Keep in mind that none of these tests can spot a lab diamond versus a natural diamond. Only equipment at diamond labs will be able to determine if a diamond is lab made. 

What Are Fake Diamonds?

If you know your diamond isn’t real, what is it? Diamond simulants include cubic zirconia, moissanite, white zircon, white topaz, white sapphire, quartz, and glass. 


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If someone shows you a diamond and says it’s real because it makes rainbow fire, don’t believe it! Many imitation stones can also refract light into rainbows–just like crystals and rainbows.

Make sure to take your stone to a trusted jeweler, or contact the Gemological Institute of America for advice. 



Lindsey graduated with an MBA in 2009. Since then, Lindsey has worked in the retail and consumer service industry as a manager, advisor, and marketer. Lindsey is also the head writer and Co-founder of Lindsey is based in Morgantown, West Virginia.

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