The Truth About Diamond Testers: Functionality, Accuracy, & Reliability Revealed! | The Diamond Gurus | DMIA (2023)

There are many ways to determine if a diamond is real or fake, but most of these methods are not always reliable. One of the fastest and most accurate ways to check if a diamond is real or fake is by using a diamond tester.

A diamond tester will tell you if the gem is real by measuring the amount and speed through which electricity travels through the stone. Diamond detectors can also use thermal conductivity which measures the amount and speed through which heat travels through the stone.

A diamond tester can help you determine the authenticity of your diamonds in just seconds. Here’s what you need to know about using a diamond tester and how to pick the right one.

The Basics of a Diamond Tester Device

A diamond tester is a portable device that can be used to test if a diamond is real or fake. It has a needle-like tip that you touch to stone. If the diamond is real, the tester will display a value and/or sound a signal.

There are two different types of diamond testers: electronic and thermal. Electronic diamond testers use electricity to test for diamonds, while thermal diamond testers measure the heat conductivity of the stone.

How a Diamond Tester Works

Diamond testers use heat or electrical conductivity to measure the authenticity of a diamond. They measure how fast heat or electricity moves through a stone. A diamond conducts heat/electricity differently than moissanite or cubic zirconia.

A diamond tester will tell you if a stone is a genuine diamond by detecting the rate at which heat/electricity travels through it.

What Diamond Testers are Commonly Used For

Many jewelers use diamond testers to check if a diamond is real or not.

If you’re thinking about selling or trading an old diamond, the jewelers will want to make sure it’s authentic. At times, it might be difficult to determine whether a stone is real or fake just by looking at it.

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Before repairing jewelry, it is important for a jeweler to know what the stone in the setting is. Different gemstones tolerate heat, pressure and stress differently, so it is important to know this before repairing the jewelry.

When you are getting your diamond jewelry repaired, it is a good idea to ask the person who is repairing it to test the stones in front of you.

If you are not sure if your gemstone is a real diamond, you can take it to a jewelry store and ask them to test it for you.

Accuracy and Reliability

Diamond testers are not 100% accurate. However, they are one of the most reliable ways to test for diamonds.

Testers that use thermal conductivity may mistakenly think that moissanite is a diamond because of how they conduct heat the same way.

In this case, it’s better to use a diamond tester that tests electrical conductivity. Diamond and moissanite have different levels of conductivity, so this method can be used to distinguish between the two.

So, it is important to get your stone tested by more than one method if you want to be sure.

Key Features to Look For in a Diamond Tester

Before you buy a diamond tester, make sure that you’re getting the right one. There are two key features that you should look for in a good diamond tester.

  1. Electrical Conductivity Testing: Make sure that the device you’re buying uses electrical conductivity to determine if a diamond is actually moissanite. The latest models on the market combine this feature thermal conductivity for better accuracy.
  2. Detecting Metal: If you accidentally touch the metal setting on a ring instead of the stone, it will give you a warning signal. Without this feature, it could signal a false/positive for diamond! Even if the diamond isn’t actually real.

People Also Ask

Do Diamond Testers Really Work? Are they legit?

Portable diamond testers actually do work and have proven to be very handy if you don’t know the authenticity of a diamond. A basic diamond detector uses its heated needle tip made of metal to cause a heat transference once placed on the diamond’s surface (thermal conductivity). You will then get a result that will let you know if the diamond is real or fake.

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The science behind a diamond tester is that heat or electricity transfers through other elements like glass or a fake diamond like cubic zirconia differently than the way it would pass through that of a real diamond. They are extremely accurate and will save you much time and effort when you are testing diamonds.

What Type of Diamond Tester is Better? Heat or Electric?

If you are thinking of purchasing a diamond tester, what type is the best choice? Of the two different tools, research has shown that electrical conductivity diamond testers are much better than thermal conductivity diamond testers. They are higher in price, but much more accurate. Heat testers are much cheaper but their accuracy is not as high, so may not get as good results.

If you will be detecting up to several diamonds a day or you are a professional jeweler, make sure to buy a diamond tester that uses electrical conductivity for high accuracy. Why? Because there is one type of “fake diamond” called moissanite that can only be detected with electricity.

If you use an electrical conductivity tester you will be sure to get a correct answer.

Is a diamond tester worth it?

I think a diamond tester is definitely worth it if you are in the market to buy diamonds or other gemstones. They will save you a lot of money and time when testing for authenticity. The last thing you want is to be sold a fake diamond!

Do diamond testers work on all diamonds?

Yes, diamond testers work on all diamonds. However, they are not 100% accurate and may not detect all fake diamonds.

What stones will pass a diamond tester?

Natural Diamonds and Lab-Grown Diamonds will pass a diamond tester. Depending on the tester you purchase, some testers can test for all stones while others are only meant for specific types of stones. For example, the Presidium Multi Tester III can test for diamonds, moissanite, and other gemstones.

What is a good diamond tester to buy?

A good diamond tester to buy is an electrical conductivity diamond tester. They are higher in price, but much more accurate. Heat testers are much cheaper but their accuracy is not high, so may not get as good results. Looking for the best diamond testers? We reviewed the top 5 diamond testers here.

Will Diamond Testers work on Ruby or Real Gem Stones?

Yes! A diamond tester will also work on ruby or and other real gemstones. A diamond tester uses the same technology to detect if a gemstone is truly real. Diamond testers not only work on diamonds and rubies but all other types of jewelry and stones. You can test stones like emeralds and sapphires as well to see whether they are real or fakes.

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Rubies can actually be very difficult to detect from garnets especially if they are darker in color. So diamond testers really come in handy in that situation. Just because a ruby is dark in color doesn’t necessarily mean that it is a fake.

Can fake diamonds pass diamond tester?

No, all fake diamonds will not pass the diamond tester. The tester is designed to determine the difference between a real and fake diamond. It does this by sending a signal through the stone being tested. If the stone being tested is a fake, the signal will not be able to pass through it like it would a real diamond.

How can Jewelers test if a diamond is real?

The three main tests that jewelers use to determine if a white stone is a diamond are confirming that the stone is singly refractive, has a hardness of 10/10, and is highly conductive.

Moissanite is easily separated from diamond under magnification because it is doubly refractive. When using a pen tester, cubic zirconia, white sapphire, and white topaz cannot effectively conduct electricity.

Additionally, most diamond simulants have low hardness and this can be seen with a magnifier.

Lab-Grown Diamonds versus Diamond Testers

Will Lab-Grown Diamonds pass a Diamond Tester?

Diamond testers can not detect a lab-grown diamond because lab diamonds are comprised of the same chemical makeup as real diamonds. Natural diamonds have the same physical elements as lab-created stones. Even to a very well-trained jeweler’s eye, lab-created diamonds will pass any diamond test and cannot be told apart from earth-mined diamonds.

How do you test a lab grown diamond?

Lab-grown diamonds have the same chemical makeup as real diamonds, so they will test as diamonds with all diamond testers. Some jewelers have specialized equipment that can determine if a diamond is lab-grown or natural. Here is a video that explains the process.

Why is my lab diamond testing as Moissanite?

If you are testing a lab diamond and it is coming up as moissanite, there could be a few potential issues. The most likely possibility is that you are using a thermal conductivity tester instead of an electrical conductivity tester. Moissanite is the only fake diamond that can be detected with thermal conductivity, so if you are not using the correct type of tester, you will get this result. Another potential issue could be that your diamond is not a real diamond. It’s best to double check with another tester, an electrical one, before you start to panic.

Moissanite versus Diamond Testers

Can a diamond tester detect moissanite?

The answer is yes. A diamond tester will detect moissanite because it uses electrical conductivity.

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Is there a moissanite tester?

Yes, there are some diamond testers that light up if they detect moissanite. Looking for the best moissanitetesters? We reviewed the top 5 moissanitetesters here.

How do you test for diamond and moissanite?

The best way to test for diamond and moissanite is to use an electrical conductivity tester. The higher-end diamond testers will be able to tell the difference between diamond and moissanite.

Cubic Zirconia versus Diamond Testers

Can Cubic Zirconia pass a diamond tester?

No, cubic zirconia will not pass a diamond tester because it does not conduct electricity. A thermal conductivity tester will also work on cubic zirconia.

How can you tell a real diamond from a cubic zirconia?

The best way to tell a real diamond from a cubic zirconia is to use a thermal conductivity tester. Cubic zirconia will not conduct electricity, so it will not pass a diamond tester.

White Sapphires versus Diamond Testers

Do white sapphires pass a diamond tester?

No, white sapphires will not pass a diamond tester. Diamond testers work by detecting the thermal conductivity of the stone being tested. Sapphires have a different thermal conductivity than diamonds, so they will not register as diamonds on a diamond tester.

How could you tell a white diamond from a white sapphire?

If you’re a jeweler, you have special tools, called gemologists’ loupe, that can help you tell them apart. But what if you’re not a jeweler? Here’s a little trick: get a white sapphire and put it next to a halogen lamp. If the stone starts to glow red, it’s a sapphire. If it doesn’t, it’s a diamond.

Or you could use a diamond tester. The best way to tell the difference between a white diamond and a white sapphire is to use a thermal conductivity tester. White sapphires will not conduct electricity, so they will not pass a diamond tester.

Final Notes on Detecting Fake Diamonds

There are many methods and ideas out there for how to tell if a diamond is fake or not. It’s smart not to leave it up to chance though because these procedures or methods are not completely accurate. An electrical conductivity diamond tester will give you an accurate fast result every time and will never let a real diamond or gemstone slip through your fingers again!

Here are some other resources I have written about spotting fake diamonds:

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  • What are Fake Diamond Rings? (9 Tips to Avoid a Fake)
  • How To Tell if a Diamond Earring is Real
  • What Types of Fake Diamonds Are There?
  • What are the Best Looking Faux Diamonds?


How reliable are diamond testers? ›

Are Diamond Testers Accurate. Diamond testers are perhaps the most accurate and reliable instruments to test the authenticity of a diamond. However, testers that measure thermal conductivity cannot tell an authentic diamond from moissanite because these gems are similar in heat transfer.

What is the most reliable diamond tester? ›

Best Diamond Testers: Which One Should You Use?
  • KKMoon Diamond Selector II V2 – Cheapest Diamond Tester Pen.
  • Presidium DiamondMate-C Electronic Tester – Most accurate Diamond Detector.
  • Presidium Refractive Index Meter II PRIM II – Best Diamond Tester.
Oct 25, 2022

How can you tell a fake diamond tester? ›

Most diamonds will reveal blue florescence under a black light; therefore, you'll see a medium to strong color of blue, which means the diamond is real. If you don't see the blue color and instead see a slight green, yellow or gray fluorescence then this usually indicates the gem is not a real diamond.

Do diamond testers work on lab diamonds? ›

Yes, lab diamonds have the same carbon composition as natural diamonds. Therefore, they have the same thermal conductivity. The test results are positive when exposed to the diamond tester, since the diamonds have the same physical and chemical properties as natural diamonds.

What diamond tester do jewelers use? ›

The GIA iD100 distinguishes simulated and laboratory-grown diamonds from natural diamonds. It is able to test colorless to near-colorless, blue-to-green and brown diamonds.

How do jewelers tell if diamonds are real? ›

A loupe is a small magnification device used by jewelers to see minute details up close. Most jewelers use loupes to inspect diamonds for their class and clarity. If you don't have one then you're in luck, as Amazon has a huge selection of loupes at reasonable prices.

Can a diamond tester tell the difference between lab and natural? ›

Yes! Lab grown diamonds test positive on a diamond tester because they're made of crystallized carbon, just as mined diamonds are.

Are all diamond testers the same? ›

The market today offers numerous types of diamond testers. The different types include: The Conventional or Thermal Diamond tester. Electrical conductivity diamond tester.

Can moissanite pass a diamond tester? ›

Unlike faux diamonds and other gemstones, moissanite is also an effective conductor of heat. For this reason, when using a diamond tester that detects thermal conductivity, moissanite will pass as a diamond.

What color does a diamond tester turn if it's real? ›

Interpreting the Results of the Test:

If LED lights up to the red zone with three periodic bees, the stone being tested is a diamond. If LED lights up only to the green and/or yellow zone, then the stone is a stimulate or non-diamond.

What is 1 carat diamond worth? ›

On average, the retail price for one carat diamonds can be anywhere between $2,000 to $16,000, and between $8,000 to $72,000 for two carat diamonds . And of course, the retail price and the resale value of a diamond are very different things.

Is there a free app to tell if a diamond is real? ›

Khanna Gems has launched a comprehensive mobile app available on both iOS & Android Platforms. The app will focus on providing authentic information to customers so that they can make an informed decision on every purchase of a gemstone or a piece of jewellery through the app.

Do lab created diamonds hold value? ›

While the market for lab-grown diamonds isn't as large or powerful as earth mined diamonds, there is still a resale value for lab-grown diamonds. The resale value typically depends on the carat and quality of the diamond. But it also depends on the commodity market for diamonds which is constantly fluctuating.

How long do simulated diamonds last? ›

Lab diamonds really do last forever, and there's nothing that will dull the shine or interfere with the brilliance of synthetic diamonds. It's not for nothing that they say it's impossible to tell the difference between a natural diamond and a man-made one.

Do lab created diamonds turn yellow? ›

No need to worry about your ring turning yellow. Your lab diamond will stay as white as it is forever. Because it's a real diamond, you can trust that it's as durable as its mined counterparts. It will never turn yellow or change color over time.

Do black diamonds pass diamond tester? ›

No, diamond testers do not test black diamonds. A diamond tester only detects white diamonds. Black diamonds are opaque, even if you use a high-quality diamond tester in it, the result may be inaccurate.

Are lab grown diamonds real? ›

Are Lab Diamonds Real? Oh yes. Lab Grown Diamonds are just as real as diamonds that are mined from the earth. They have shape, size, color and clarity grades, just like Natural Diamonds.

Will moissanite pass a diamond tester? ›

Unlike faux diamonds and other gemstones, moissanite is also an effective conductor of heat. For this reason, when using a diamond tester that detects thermal conductivity, moissanite will pass as a diamond.


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