The most reliable way to tell if a diamond is real is to have it examined by an experienced jeweler or gemologist using professional testing equipment. While there are a few at-home tests that can give you clues, they cannot definitively authenticate a stone. This is especially important today because natural diamonds, lab-grown diamonds, and diamond simulants can look remarkably similar to the untrained eye.
At Adam Foster Fine Jewelry, we spend a lot of time looking closely at gemstones. Whether you've inherited a piece of jewelry, found an old ring tucked away somewhere, or you're considering buying a diamond, knowing exactly what you're looking at matters. And sometimes, the answer isn't as simple as "real or fake."
What Does a "Real Diamond" Actually Mean?
Before testing anything, it's helpful to clear up one common misconception: lab-grown diamonds are real diamonds.
Both natural and lab-grown diamonds are made of carbon arranged in the same crystal structure. The primary difference is where they formed. Natural diamonds formed deep within the Earth over an extremely long period of time, while lab-grown diamonds are created in controlled laboratory environments using technology that recreates the conditions needed for diamond growth.
A diamond simulant is different. These stones may resemble diamonds, but they have different chemical and physical properties.
Some of the most common materials you may encounter include:
- Cubic zirconia (CZ)
- Moissanite
- White sapphire
- Glass
So, when someone asks us, "Is this diamond real?" there are actually two questions we may need to answer: Is the stone a diamond, and if it is, is it natural or lab-grown?
Common Myths About Spotting a Fake Diamond
Diamonds invite plenty of folklore, and a surprising amount of it gets repeated as fact.
"If it scratches glass, it's a diamond." Other hard materials can scratch glass, and deliberately scratching things with your diamond is a bad testing strategy.
"If it has inclusions, it must be natural." Both natural and lab-grown diamonds can contain inclusions.
"A fake diamond will look fake." High-quality simulants can be convincing, particularly to someone without gemological training.
"Lab-grown diamonds are fake diamonds." They aren't. Lab-grown diamonds are diamonds; their origin differs from naturally formed diamonds.
"If my diamond tester says diamond, I know exactly what I have." A basic tester has a much narrower job. It does not necessarily tell you whether a diamond is natural or lab-grown, nor does it grade its quality.
Can You Tell If a Diamond Is Real Just by Looking at It?
Sometimes there are visual clues, but appearances alone aren't enough to authenticate a diamond.
A trained jeweler can examine a stone under magnification and look for characteristics that provide information about its identity and quality. Natural diamonds, for example, may contain inclusions that formed as the diamond developed within the Earth.
But inclusions aren't an automatic test for a natural diamond. Lab-grown diamonds can have inclusions, too, and some natural diamonds have such high clarity that their inclusions may be extremely difficult to see.
Likewise, assuming a stone is fake because it looks "too perfect" isn't reliable.
Look at the Setting, Too
If you're examining a diamond that's already set in a piece of jewelry, look at the jewelry surrounding it.
Precious metals such as 14K or 18K gold and platinum are commonly marked with identifying stamps. Finding a quality gemstone in a fine-jewelry setting is certainly more plausible than finding one in inexpensive costume jewelry.
However, the setting cannot authenticate the stone. Real diamonds can be reset into all kinds of jewelry, and simulants can be placed in precious metals.
Think of the setting as another clue rather than proof.
At-Home Tests for a Real Diamond
If you're curious about a stone you already own, you've probably encountered a long list of DIY diamond tests online. Some can reveal differences between materials, but none should take the place of professional authentication.
Here are some of the most common.
1. The Fog Test
The fog test involves breathing onto a diamond as you would a mirror and watching how quickly the condensation disappears.
Diamond conducts heat efficiently, so the fog should generally dissipate quickly. A material that retains condensation for longer may not be a diamond.
The problem is that environmental conditions, the cleanliness of the stone, and other materials can affect the result. It is an interesting experiment, but we wouldn't make a financial decision based on it.
2. The Water Test
Another popular DIY method involves dropping a loose stone into a glass of water. Because diamonds have a relatively high density, a diamond should sink.
Unfortunately, plenty of things that aren't diamonds sink in water, too.
The water test can therefore tell you that your stone sinks. It cannot reliably tell you that your stone is a diamond.
And if your gemstone is mounted in jewelry, skip this test altogether.
3. The Newspaper or Dot Test
For this test, a loose diamond is placed over printed text or a small dot. The idea is that a properly cut diamond refracts light in a way that makes it difficult to clearly see the print through the stone.
Again, there are limitations. Diamond shape, cut, proportions, and orientation can all affect what you see.
It's another clue, not a certification.
Can You Test a Diamond by Scratching Glass?
You've probably heard this one: "Diamonds are the hardest material, so if it scratches glass, it's real."
Please don't test your jewelry this way.
Diamonds are extremely hard and rank 10 on the Mohs scale of mineral hardness, but other materials can scratch glass as well. More importantly, hardness refers to resistance to scratching. It does not mean a diamond is impossible to chip or damage.
Trying to prove that a diamond is real by scraping it against another surface introduces unnecessary risk to both the stone and whatever you're scratching.
Your jewelry doesn't need to pass an obstacle course to prove itself.
Real Diamond vs. Cubic Zirconia
Cubic zirconia is one of the best-known diamond simulants. It can be colorless and highly reflective, making it an inexpensive way to achieve a diamond-like appearance.
However, cubic zirconia and diamond are different materials.
CZ tends to be heavier than diamond when comparing stones of similar dimensions. It also interacts with light differently and is considerably softer than diamond.
An experienced professional may spot clues under magnification, but don't assume you can identify CZ simply because a stone seems unusually sparkly or flawless.
Diamond vs. Moissanite
Moissanite makes home identification considerably trickier.
Moissanite is a gemstone in its own right, but it is also frequently used as a diamond alternative. It is very durable and can look similar enough to diamond that visual inspection by an inexperienced observer isn't dependable.
One difference is how the materials interact with light. Moissanite can display more colorful flashes, sometimes described as a "rainbow" effect, while diamond has a different balance of brilliance and fire.
But that's not a reliable home test either.
Even some basic thermal diamond testers can have difficulty distinguishing between diamond and moissanite. Professional jewelers can use additional testing methods to determine which material they're examining.
Natural vs. Lab-Grown Diamonds Can Be Even Harder to Identify
This is where the idea of "I'll just look closely at it" really falls apart.
You generally cannot determine whether a diamond is natural or lab-grown simply by looking at it with the naked eye. Both are diamonds, and both can have excellent color, clarity, and cut.
Even traditional diamond-testing methods may simply confirm that the stone is a diamond rather than establishing its origin.
Distinguishing natural from laboratory-grown diamonds can require specialized equipment that examines characteristics associated with how the diamond grew.
If knowing the diamond's origin matters to you, professional verification and appropriate grading documentation are far more useful than an at-home test.
What About a Diamond Tester?
A handheld diamond tester is more useful than dropping your jewelry into water, but it still has limitations.
Traditional testers commonly rely on thermal conductivity. Because diamond conducts heat exceptionally well, the instrument measures how the stone responds and uses that information to help identify it.
More sophisticated testers may use electrical conductivity in addition to thermal testing, which can help distinguish diamond from materials such as moissanite.
The quality of the tester matters. So does knowing how to use it.
A positive reading should therefore be considered one piece of evidence rather than a complete evaluation of the diamond's identity, origin, or quality.
How Professionals Tell If a Diamond Is Real
Professional authentication goes much further than a single pass/fail test.
A jeweler or gemologist can examine the stone under magnification, evaluate its physical and optical characteristics, and use appropriate instruments to determine what type of gemstone you're dealing with.
Depending on the situation, that may include:
- Microscopic examination
- Thermal and electrical conductivity testing
- Specialized screening for natural and lab-grown diamonds
- Examination of inscriptions and existing documentation
For particularly important or valuable diamonds, an independent gemological laboratory can provide formal grading and identification.
Does a GIA Report Prove a Diamond Is Real?
A grading report from a respected gemological laboratory can provide much more useful information than an at-home test.
The Gemological Institute of America (GIA), for example, evaluates diamonds and issues reports containing information about their characteristics. Depending on the type of report, this can include measurements and the familiar 4Cs: cut, color, clarity, and carat weight.
Some diamonds also have microscopic report numbers inscribed on their girdles. That inscription can be compared with the corresponding report, although the stone itself should still be verified when authenticity is in question.
A grading report isn't the same thing as an appraisal, either. A grading report describes and evaluates the gemstone; an appraisal generally addresses monetary value for a particular purpose.
Buying a Diamond With Confidence
If you're shopping for a diamond rather than examining one you already own, you can save yourself a lot of uncertainty by paying attention to who is selling it.
Ask what you're buying. Is the diamond natural or lab-grown? Does it come with a grading report? Which laboratory graded it? What are its cut, color, clarity, and carat weight?
You should feel comfortable asking questions and getting understandable answers.
A diamond is too personal, and often too significant of a purchase, for the details to feel mysterious.
When Should You Take a Diamond to a Jeweler?
If the answer actually matters, take it to someone who knows what they're looking at.
That is particularly important if you've inherited jewelry, are considering redesigning an heirloom, want to insure a piece, or are thinking about buying or selling a diamond.
Professional evaluation can help determine what the stone actually is before you make decisions around it.
At Adam Foster Fine Jewelry in Frontenac, our team works directly with diamonds and fine jewelry every day. If you've inherited a piece and have no idea what you're looking at, that's okay. Bring it in. We can take a closer look, talk through what you have, and help you understand your options without relying on tricks you found online.
Frequently Asked Questions About Real Diamonds
Can you tell if a diamond is real with the naked eye?
Not reliably. Some stones have characteristics that may provide clues, but natural diamonds, lab-grown diamonds, and convincing simulants can be difficult to distinguish visually. Professional testing is the safer option.
Do real diamonds sparkle rainbow colors?
Diamonds can produce colorful flashes known as fire, along with white-light brilliance. However, sparkle alone cannot authenticate a diamond because other gemstones and simulants also interact dramatically with light.
Will a real diamond sink in water?
A loose diamond should sink because of its density, but so will many other materials. The water test cannot prove that a stone is a diamond.
Are lab-grown diamonds considered real diamonds?
Yes. Lab-grown diamonds have the same fundamental crystal structure and chemical composition as natural diamonds. The primary distinction is their origin.
Can a jeweler tell the difference between a diamond and cubic zirconia?
Yes. A jewelry professional can use magnification and gemological testing methods to distinguish a diamond from cubic zirconia and other simulants.
Can a jeweler tell if a diamond is lab-grown?
Determining origin can require specialized screening because natural and lab-grown diamonds are both diamonds. When necessary, further testing by a gemological laboratory can provide definitive identification.
What should I do if I inherited a diamond without any paperwork?
Don't assume the stone's identity or value based on family history alone. Have the jewelry professionally examined. Once you know what you have, you can make a more informed decision about wearing it as-is, insuring it, or incorporating the stone into a new design.
What's the safest way to find out if my diamond is real?
Skip potentially damaging DIY tests and have the stone evaluated by a qualified jewelry professional. You'll get a much more useful answer, and your jewelry won't have to scratch a drinking glass to get it.