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How to Tell if Diamonds are Real

Updated on April 6, 2015

Diamonds are probably the most coveted gemstone of all time. From engagement rings to stud earrings to flashy drop pendants, there is no doubt that diamonds are the most popular and most luxurious gemstone of all time. Of course, that also means that diamonds are incredibly expensive!

Due to their expense and massive popularity, there is a huge market of imitation and "fake" diamonds. Some people choose to purchase imitation diamonds rather than the real thing to save on cost while some shady retailers try to pass fake diamonds off as real to make a larger profit.

If you are in the market to purchase a diamond (or just received one as a gift) and you want to make sure the stone is the real thing, follow these steps below to determine whether or not a diamond is real.


First and foremost, do not purchase a diamond unless it comes with a certificate of authenticity. Additionally, if you receive a diamond as a gift, you should ask the gift giver for the certificate of authenticity as you will need it for insurance.

You want the certification of authenticity to come from an impartial diamond grading authority such as GIA, AGSL, EGL, PGGL. The certification can also come from an independent appraiser who is affiliated with a professional organization, but the grading authorities are your best bet.

Tip: You never want to buy a diamond site unseen (such as from the internet) without a valid certification from a reliable source, odds are the stone will be fake or of lower quality than the seller claims.


Look Through the Stone

Diamonds have a high refractive index which means that any light that passes through them will bend sharply. On the other hand, glass and quartz have a low refractive index; therefore, they sparkle less because they bend the light less. One step to determine whether a diamond is real or not is to look through the stone and see how light passes through it.

Unmounted Stones
If you have a loose diamond and are trying to figure whether it is real, turn it upside down and place it on a piece of newspaper or a book.

If you can read the print through the stone or if you see distorted black smudges, the stone is likely fake.

If the stone shows signs of double refraction, it may be Moissanite. Moissanite is a gemstone often used to imitate diamonds because it shares many characteristics with diamonds and frequently even jewelers can't tell the difference between diamonds and Moissanite.

Another test to determine whether a stone is actually a diamond is to draw a small dot on a piece, place the stone over the center of the dot, and look directly down on it. If you see a circular reflection in the stone, the stone is not a diamond.

Mounted Stones
If the stone is mounted in a ring or other setting, you should not be able to see the bottom of a diamond when looking directly at it from the top.



Another way to test whether a diamond is real or not is to weigh the stone.

Use a carat or gram scale to weigh the stone and compare its weight to the weight of a diamond that you know is real that is similar in size to the stone you are testing.

Fake stones such as cubic zirconia weigh about 55% more than real diamonds that are the same shape and size.


Check the Mount and Setting

When trying to determine whether a diamond is real or not, if it is not a loose diamond but rather set in a ring, necklace, earrings, etc.... you should evaluate the setting to try to determine whether the diamond is real or not.

Likely, someone is not going to spend the money to set a fake diamond in precious metals and will instead likely set a fake stone in a cheaper imitation metal. Similarly, a real diamond will likely not be set in cheap metal.

For rings, look at the stamps inside the setting. Stamps of 10K, 14K, 18K, 585, 750, 900, 950, PT, or Plat indicate real gold or platinum. Meanwhile, a "C.Z." stamp will immediately give away that the stone is a cubic zirconia and therefore, fake.

UV Light

An ultra violet (UV) light can be used to evaluate whether a stone is a real diamond or not. Diamonds will often exhibit blue fluorescence under an ultra violet light. Therefore, the presence of a medium to strong blue when a stone is placed under a UV light will confirm that it is a real diamond.

However, not all diamonds exhibit a blue fluorescence under a UV light. Therefore, the absence of blue does not mean the stone is fake. In fact, the higher the quality diamonds the less likely it will exhibit blue fluorescence.

If you see a very slight green, yellow, or gray fluorescence under the UV light, the stone may be Moissanite.

Heat Probe

Another way to determine whether a stone is a real diamond or not is to test it with a heat probe.

Real diamonds disperse heat very quickly and therefore won't get hot from a heat probe. Whereas fake stones will get warm from the heat probe.

To test a stone with a heat probe, simply apply the probe to the stone for about 30 seconds and don't worry! The heat probe will not hurt the stone in any way.


You can also use an x-ray to determine whether a stone is a real diamond or not.

Real diamonds will not show up on an x-ray.

Glass, cubic zirconium and crystals all have slightly radiopaque qualities which means that they will show up on an x-ray.

Jeweler's Loupe

A common test to determine whether a stone is real and to evaluate the quality of a diamond is to use a jeweler's loupe to inspect the stone.

Mined diamonds usually have small imperfections or inclusions that can be seen when looking at the stone through a jeweler's loupe whereas cubic zirconium and other fake stones do not have imperfections.

Additionally, lab-grown diamonds--which should pass the other tests because they are diamonds--usually don't have imperfections so if you want a mined diamond rather than a lab created diamond, this is a great way to evaluate whether a diamond is lab-grown or mined.

Water Test

The water test is another way to determine whether or not a stone is a diamond or not.

If you place the stone in water and it sinks, it is real. If it floats, it's likely fake.

Fog Test

Another test to determine whether a stone is a diamond or fake, is the fog test.

Place the stone close to your mouth and breathe on it.

If the stone stays "foggy" for 2-4 seconds it is not real. Real diamonds will have cleared by the time you look at them.

Diamond Tester

Don't trust any of the other methods? You can purchase a diamond tester that is relatively inexpensive. Diamond testers will determine whether a stone is a real diamond or a simulant.

You can find an example of a diamond tester that you can purchase on Amazon below.

What Do You Prefer Real or Fake Diamonds?

Do you prefer real or fake diamonds? Share your reason below in the comments

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