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How Much Is A Diamond Tester?

How Much Is A Diamond Tester?

Diamond testers are an excellent tool for verifying if the stone you’re holding is a real diamond or just a good-looking fake. Whether you’re looking to buy or sell a precious stone, you’re likely to come across one of these gadgets.

But given the critical role it plays, how much is a diamond tester?

Generally, the price for diamond testers ranges anywhere between $20 and $200, depending on the model’s quality and extra features that it might include.

And since it will help you determine if the diamond is real or not, we’d say that’s a reasonable price to pay for this gadget. 

However, that’s not the only thing you should know about diamond testers. How do they work? Are they reliable? Can you test diamonds using different methods?

Don’t worry; these questions are covered in this article. So, without further ado, let’s learn more about these diamond-testing gadgets!

What Are Diamond Testers?

The name explains it pretty well – diamond testers are designed to test diamonds. 

A diamond tester is a portable gadget that can fit in your pocket and features a small tip that is placed on the stone’s surface to have it tested. 

If the stone is a real diamond, the tester will indicate that on its display or with a sound signal.

How Diamond Testers Work?

Diamond tester’s method of operation is based on the fact that different gems conduct heat – or in some cases, electricity – differently.

When you put the needle of a diamond tester onto the precious stone’s surface, the heat passes through the stone. 

However, the heat (or electricity) passes through diamonds differently than, for example, cubic zirconia. The tester detects the rate at which heat moves through the stone and tells you whether it’s a genuine diamond or not.

We’ve already indicated this, but it doesn’t hurt to point it out once again: There are also diamond testers that use electrical conductivity to test gemstones – their principle of operating is similar, but they use electricity instead of heat.

Learn More: How Does A Diamond Tester Work?

How Reliable Are Diamond Testers?

Diamond testers are among the most accurate gadgets to check a diamond’s authenticity. That doesn’t mean that they don’t make mistakes, though.  

It’s worth noting that diamond testers that rely on thermal conductivity could confuse moissanite for a diamond. Why? 

Well, these two gemstones have relatively similar heat-conducting properties, making it harder for the tester to recognize which stone is being tested.

Don’t worry, though; there’s a way to fix this – by using a diamond tester that relies on electrical conductivity. 

If the device tests the electrical conductivity of the gemstones, moissanite, and diamonds are much easier to tell apart because they conduct electricity differently.

Learn More: Can Diamond Testers Be Fooled?

What Makes A Good Diamond Tester?

If you’ve decided that you want to get a diamond tester, there are a few things you have to take into consideration before you buy one.

First, make sure that the tester uses electrical conductivity and heat conductivity. That way, you will be able to tell moissanite from diamonds – and genuine diamonds from fakes. 

The latest diamond tester models on the market combine heat and electricity testing to ensure improved accuracy. That’s what you should aim for, too.  

Another feature found in specific diamond testers is the included metal detector that signals if you touch the part of the metal setting by accident.

Why is this important? Well, suppose your diamond tester doesn’t recognize metals. In that case, it could give you a false reading – either a positive or negative one – because you unknowingly placed the needle on the setting rather than the stone.

Yes, it happens – more often than you realize.

Of course, you should expect to pay a bit more for this handy feature – especially if the diamond tester you buy can detect both heat and electrical conductivity.

Handy Diamond Tester Features

If you wish to buy a diamond tester, you should take a moment to consider some additional features – beneficial ones, might we add – that you might want your model to include. Again, the extra functionality might affect the price, but it will be worth it in the long run. 

You’ll be using this gadget to test precious stones; spending a bit more on a diamond tester is a good deal if it means it will save you from spending thousands of dollars on a fake gem. 

With that said, let’s see what else they have to offer. 

1. Retractable Tip

The tips of these gadgets are incredibly delicate, as they have to be highly sensitive to do their job.

That’s why you want to look for a tester with a retractable tip. It’ll ensure you apply the correct amount of pressure to the diamond’s surface.

That way, the tip protects itself from human error. In addition, you won’t need to spend extra money on repairs or replacement if it gets broken.

2. Quick To Reach Testing Temperature

Traditional diamond testers tell diamonds apart from other gemstones by measuring the stone’s thermal conductivity.

As the tip of the diamond tester heats up, you place it against the room-temperature gemstone’s surface. Heat is transferred from the warmer diamond tester’s tip to the cooler gem when you do that. 

And based on this process, the tester gains a thermal conductivity reading.

So, if you’re testing multiple gemstones in one sitting, you would want a tester that reaches and returns to working temperature reliably and quickly. 

That way, previous readings won’t mess with the future tests when you do them back-to-back. 

3. Battery Or Mains Powered

The power source essentially determines the portability of your diamond tester. You’ll have two options here – battery-powered or mains-powered. 

While battery-powered diamond testers give you more flexibility in terms of where you can use them, it wouldn’t hurt to have the alternative option to hook it up to the mains.

Some models offer both of these options. So, keep that in mind as you check the product specs.

4. Ease Of Use 

If you’re new to all this and haven’t used a diamond tester before, you’d obviously benefit from a model that’s straightforward to use. Who wants to spend hours setting the device up or figuring out how it works? 

Ideally, all it should take to start testing is a flick of a switch. Turn it on, place the probe in direct contact with the gem, and let it do its thing; it’ll notify you via visual or audible signals about the results. 

That’s how simple the whole process should be. 

Related Read: What Happens When A Diamond Tester Beeps?

When Are You Likely To Need A Diamond Tester

If you’re purchasing, selling, repairing, or loaning diamond-embedded jewelry, the chances are that you’ll come across a diamond tester sooner or later. Here are three example scenarios of when you might need one. 

Selling Or Loaning

Suppose you want to sell or loan a diamond. In that case, the standard practice for the diamond dealer you’re doing business with is to use a diamond tester to verify the stone’s authenticity.

That way, they can ensure the diamond’s quality before making you an offer. It’s a standard part of doing business in the jewelry world. 


If you’re looking to buy a diamond, you might want to ask the seller or jeweler to test the gems you’re considering right in front of you.

That way, you’ll be sure that you’re getting a good deal for a genuine diamond – and not just a nice-looking fake.


When you take your diamond jewelry for repair, more often than not, it’ll be out of your sight while jewelers take care of it in their workshop.

Call us paranoid, but it’s worth testing the repaired piece when you come back to pick it up. The whole diamond-switching thing is a real risk. 

So, be sure to ask the jeweler to test it right in front of you. They should be more than happy to do so as part of their professional service.

How To Test Diamonds At Home

While diamond testers are a great tool for verifying the diamond’s authenticity, there are several simple tricks you can do at home to test if your stone is a genuine diamond or not. 

The best part of these is that they’re all free!

Water Test

Grab a glass, fill it with water – and carefully drop the gemstone into it.

If the stone sinks, it’s a real diamond. However, if the stone floats underneath or at the water’s surface, you have a fake on your hands.

A natural diamond has a high density, meaning the water test shows if your gemstone matches this high level of density or not.

Fog Test

Hold your gem between two fingers and breathe on it. The moisture and heat in your breath will cause a light fog to form on the stone’s surface.

If the for disappears right away, you have a real diamond. However, if it takes a few seconds to disappear, the stone is a fake.

Diamonds effectively conduct heat – and, thus, disperse it quickly.

Heat The Stone – And See If It Shatters

As you may know, diamonds are incredibly durable and capable of handling high temperatures.

To test this theory, fill a glass with cold water. Now, use fire-proof gloves or a set of pliers to hold the gemstone and heat it with a lighter for about 40 seconds before dropping it into the glass with cold water.

If the gemstone shatters, it’s made out of weaker components. Thus, it’s not a natural diamond – which would show no reaction.

This method tests the strength and quality of your gemstones; due to the quick expansion and contraction of the heat, weaker materials such as cubic zirconia or glass will break.

Read More: Will A Diamond Shatter If Heated?

Test A Stone At Home Using Refractivity

When you see the diamond’s sparkle, you’re experiencing its ability to refract light. Light hits the pavilion; it’s bounced around and refracts through the table to the viewer’s eyes. 

And when a diamond refracts light exceptionally well and sparkles radiantly, it’s called brilliance. Other gemstones won’t refract light that well and will have less brilliance – if any at all.

There are two tests to test a diamond’s refractivity – the newspaper test and the dot test.

To test the stone’s refractivity, place it flat side down onto a piece of newspaper in a section with lots of words. Alternatively, draw a dot with a pen on a piece of paper and use that instead of the newspaper. 

Either way, make sure the lighting is bright and that no objects cast a shadow on the stone.

If you can read words in the newspaper or see the dot – even if they’re a bit blurry – the diamond is fake. However, if the diamond is genuine, its facets wouldn’t refract light in a straight line – but rather in different directions.

Due to the diamond’s powerful refractive ability, light bounces in different directions rather than in a straight line – and that means that seeing clearly through the stone wouldn’t be possible.

Test A Diamond At Home Using Reflectivity

You can also test a diamond’s reflectivity to verify its authenticity. 

While refractivity is related to the direction of the bouncing light, reflectivity refers to the quality and amount of the light reflected off the gemstone’s table.

To test its reflectivity, use the sparkle test on the stone. How?

Hold the stone under a standard lamp and watch how the light is reflected off of its surface. Do you see bright flashes of light bouncing off of the gem? Also, do you see colorful reflections, as well?

A genuine diamond reflects white light exceptionally, providing fantastic sparkle. Diamonds also reflect colored light – also known as fire.

If you compare a genuine diamond to a fake one, you’ll be able to notice a drastic difference in the colored and white sparkle that the real one exhibits.

How To Recognize Other Gemstones That Aren’t Real Diamonds

With the rising popularity of other gemstones, here are some tips for spotting a stone that might appear similar to a genuine diamond – even though it’s not.

How To Recognize Synthetic Diamonds

With an increasing prevalence of lab-grown diamonds, knowing how to tell synthetic diamonds and natural diamonds apart is helpful. 

Lab-grown diamonds have similar molecular and chemical components to a natural diamond – they’re virtually identical in that sense. 

Because of their complex internal qualities, we recommend that you take your diamond to be inspected by a professional diamond expert. They can run all sorts of tests that you wouldn’t be able to do at home.

How To Recognize Cubic Zirconia

Cubic zirconia is one of the most straightforward fake diamonds to test authenticity-wise. 

For example, the sparkle test will relatively quickly show the amount of sparkle and fire the gem is giving off – and trust us, cubic zirconia sparkless differently. Plus, it reflects orange-tinted light. 

Furthermore, cubic zirconia weighs more than a natural diamond and typically doesn’t have any inclusions and imperfections. 

Genuine, Earth-mined diamonds will almost always have inclusions.

Related Read: Are Cubic Zirconia (CZ) Diamonds Fake?

How To Recognize White Saphire

Sapphires are available in blue and a wide range of other colors – including white. White sapphires are often posed as genuine diamonds but don’t exhibit the diamond’s signature sparkle.

If the stone seems more blurred – meaning it doesn’t have well-defined dark and light areas – it’s most likely a white sapphire.

Related Read: Diamond Vs. White Sapphire: Comparison Guide

How To Recognize Moissanite

Perhaps the best “fraud” in the diamond world is the moissanite. The distinction between a real diamond and moissanite is usually difficult for the naked eye to detect – it requires the expertise of a diamond professional.

An electrical conductivity test will indicate if the gem is a genuine diamond or just moissanite. 

But interestingly enough, thermal conductivity isn’t a valid method for recognizing moissanite because they have almost identical thermal conductivity as diamonds.

Related Read:


So, how much is a diamond tester? 

Generally, the price of a diamond tester can range from $20 to $200, depending on the quality of the model and additional features that are included.

While diamond testers are a great tool for determining the authenticity of the diamond, there are several diamond testing methods that you can do at home. And the best thing about them is that they’re completely free!

Water test, fog test, and newspaper test – just to name a few – are great methods of verifying the diamond’s authenticity. 

Ultimately, if you want to be 100% sure that your gemstone is a real diamond, we’d recommend having the diamond expert examine it. 

They can utilize professional equipment to test diamonds and give you the most accurate result.