You’re gearing up for the big proposal, and you’re starting to get cold feet. But…not for reasons you might expect. You’re worried that the beautiful engagement ring you just purchased might not have a real diamond, as advertised. How can you check? A diamond tester is one option. Not sure what that is? We’re here to tell you more!

What is a Diamond Tester?

A diamond tester is a handheld tool that evaluates how heat moves through a gemstone (aka thermal conductivity). Diamonds are known to be good heat conductors, meaning they spread heat quickly after being exposed to high temperatures. Other gems typically distribute heat more slowly. Therefore, this gadget offers an affordable, easy way to differentiate diamonds from cubic zirconia and certain other diamond simulants.

How Does a Diamond Tester Work?

Diamond testers are shaped like oversized pens, and they’re available for sale on various websites. When you’re ready to test your stone, place your finger on the back metal plate and press the tester’s metal tip on the diamond’s surface. As the device starts analyzing the gem, results are provided via a series of lights. For example, all of the lights will brighten to indicate a real diamond. The entire process takes less than a minute.

*Pro Tip: Check your diamond tester in multiple rooms to guarantee the same results at different temperatures. And if you’re experiencing long wait times between tests, you might consider purchasing a new device.

How Reliable is a Diamond Tester?

When it comes to at-home gem assessments, diamond testers are reportedly more reliable than other tricks, such as dropping your stone in a glass of water and watching how fast it falls. But you don’t want to solely rely on testers. Why? Sometimes, these gadgets have defects. And the readings aren’t always accurate. For example, testers often label moissanites as diamonds, as these stones also distribute heat quickly. However, moissanites are completely separate gems with different chemical structures, levels of sparkle, etc. So, you should ultimately check with a trusted jeweler, like Gage Diamonds, for professional testing.

What About Lab Grown Diamonds?

Since lab grown diamonds are also real diamonds, testers usually classify them just like natural stones. But due to their growth processes, they might have different crystal densities and therefore thermal conductivity levels. That means testers sometimes incorrectly read them as moissanites. Just another reason to take your gem to a reliable jeweler!

*Pro Tip: Diamond testers won’t be able to tell whether a stone is natural or lab grown. To check, you’ll need to have your diamond examined at a gemological laboratory.

Have a question? We can help!

Gage Diamonds is Chicago's premier jewelry showroom and online retailer of engagement rings, wedding bands, and fine jewelry. We offer a selection of dazzling handpicked diamonds, including certified natural and lab grown diamonds.

We’re committed to helping you find the ring of your dreams. For inspiration, browse our selection of natural and lab grown diamonds, or set up an appointment with a member of our trusted staff at our in-person showroom.

We offer no-credit-needed financing – feel free to apply and get your approval within 24 hours!

Pay over time, because love shouldn’t wait.