Whether you’ve found some loose “diamonds” or got a new engagement ring from someone you’re not too certain about, knowing how to tell if a diamond is real is a useful skill to pick up.
Below, we’ll outline several easy methods you can use to spot a fake diamond. But with a word of warning: while it is pretty easy to spot certain types of fake diamonds, some fakes like moissanite or cubic zirconia can be pretty convincing.
With that in mind, if you don’t have much experience with gemstones, the best way to confirm if you have a real diamond is to consult an expert jeweler for their opinion.
Got your diamonds ready? Good! Let’s learn how to test their authenticity.
Diamond has some exceptional heat conducting properties which most diamond alternatives lack. There are a few methods you can use involving heat to determine if the diamond is authentic.
Note that while these techniques can weed out many diamond simulants, they don’t work well for spotting moissanite as it has similar heat conducting properties to diamond.
Here are three techniques:
1. Fog Test: Clean the surface of the stone, then hold it up to your mouth and exhale on the diamond. If the fog dissipates within a second or two, it is more likely you have a real diamond. If it lingers for longer than a few seconds, you probably have a fake diamond.
2. Lighter Test: To perform this test, you’ll need a lighter, a pair of pliers, and a glass of water. Hold the stone at a safe distance with the pliers as you heat it with the lighter. After heating for around 45 seconds, drop the stone into the water. If it cracks or shatters, it is a fake diamond. Genuine diamonds will have no response to this test.
3. Diamond Tester: There are several electronic devices available that test diamonds by measuring their heat conductivity. While you probably don’t have one of these lying around, they can be easily purchased online and require no expertise to operate. However, diamond testers that rely on heat conductivity can’t discern between diamond and moissanite.
The Float Test
Probably the quickest test you can do: just toss your suspected diamond into a glass of water and see if it floats.
If it floats, you can be 100% sure that you don’t have a diamond. Diamond is much too dense to float. Cheap imitations like glass or quartz will float to the surface.
But if it sinks, you still can’t be sure if it’s a real diamond. Common diamond simulants including cubic zirconia and moissanite will also sink to the bottom. At least you know it isn’t glass!
With the help of a magnifying glass, you can examine the diamond for imperfections.
You can also get a specialized magnifying glass known as a jeweler’s loupe to make close-up inspections easier.
Real diamonds have small imperfections and flaws which are known as inclusions.
Fake diamonds lack these small flaws. A seemingly “flawless” diamond is often a clear sign that you’ve got a fake.
You can also perform a sparkle test by holding the stone under a strong light. Real diamonds give off a brilliant sparkle which is much more intense than the sparkle from diamond alternatives like cubic zirconia.
While these visual inspection methods are simple to perform, they do require something of a trained eye. It’s best to perform these tests when you have multiple stones to compare and some real diamonds which you can use as a reference.
If the stone is set in a piece of jewelry, take a close look at the setting and mount.
Diamond is an expensive material and is found almost exclusively in high-quality jewelry. Typically, it will be mounted with a material such as white or yellow gold, platinum, or in a halo setting with other gemstones.
You can examine the setting and the jewelry for any stamps or markings which indicate the material type. A marking such as 10k or 14k indicates the type of gold used, while a marking such as “PT” refers to platinum.
Imitation diamonds are often identified with markings as well. The marking “CZ” will let you know you’ve got a cubic zirconia.
A setting can also hide imperfections in the stone which make it obvious that it is not a genuine diamond. For this reason, jewelers often remove stones from the setting before inspecting or testing them for authenticity.
Now You Know! (Maybe?)
To really know what you have -- or to spot that ever deceptive moissanite -- it’s worth bringing your stones into a jeweler.
They have specialized equipment, a trained eye, and plenty of reference stones on hand to test what you have against real diamonds.