Can a Diamond Tester Test Moissanite? 2025

As someone who has spent years in the fine jewelry trade—examining diamonds, moissanite, and other gemstones under loupes, scopes, and testing devices—I’ve seen first-hand just how tricky gemstone identification can be. Many customers (and even some jewelers!) assume that a diamond tester is a foolproof tool for separating real diamonds from lookalikes. But here’s the surprising truth: most standard diamond testers can’t reliably distinguish between diamonds and moissanite.

This matters because moissanite is not just any imitation—it’s a brilliant, lab-created gemstone with optical properties so close to diamond that only advanced tools can consistently tell them apart. If you’re a jeweler, reseller, or a curious customer shopping wholesale moissanite, understanding how diamond testers work—and their limitations—is absolutely crucial.

In this article, I’ll break down the science of diamond testers, explain why moissanite often confuses them, and explore better methods for gemstone verification. Whether you’re a retailer trying to protect your reputation or a buyer wanting peace of mind, this guide will arm you with the expert knowledge you need.

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How Do Diamond Testers Work?

A diamond tester is a handheld device designed to check gemstones using either:

• Thermal conductivity (heat transfer)

• Electrical conductivity (resistance to electrical current)

• Or a combination of both

Diamonds are famous for their exceptional thermal conductivity, meaning they disperse heat quickly. When a diamond tester probe touches a stone, it measures how fast heat moves through it. If the stone transfers heat as fast as a diamond, the device signals “diamond.”

However, moissanite—though technically a different material (silicon carbide)—also has extremely high thermal conductivity. That’s where things get complicated.

Why Moissanite Can Fool Diamond Testers

Here’s the catch:

• Moissanite and diamonds both register as “diamond” on thermal testers.

• Traditional testers cannot tell them apart because their heat conductivity values are nearly identical.

• This means jewelers relying solely on a thermal diamond tester could mistakenly label moissanite as a natural diamond.

With the rise of high-quality lab-created moissanite jewelry, this overlap has become one of the biggest challenges in the gem-testing industry.

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Modern Diamond Testers: Diamond vs. Moissanite

To address this problem, newer models of testers now incorporate dual-probe technology:

1. Thermal conductivity probe – to identify diamonds vs. simulants like CZ.

2. Electrical conductivity probe – to detect moissanite (which conducts electricity, unlike diamonds).

Some advanced testers even combine optical detection for higher accuracy. These multi-functional diamond & moissanite testers are now considered the professional standard in jewelry stores.

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Professional Testing Methods Beyond Diamond Testers

Even with modern devices, professionals often use multiple methods to confirm gemstone identity:

1. Loupe Examination

Moissanite shows a telltale double refraction, visible under magnification. Diamonds do not.

2. UV Fluorescence

Some diamonds fluoresce under UV light, but moissanite usually does not (or reacts differently).

3. Specialized Lab Equipment

• Spectroscopes

• Refractometers

• Gemological laboratory reports (GIA, IGI, etc.)

These methods provide definitive authentication, especially important for wholesale jewelry businesses.

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Why It Matters for Wholesale Buyers and Retailers

If you’re purchasing moissanite jewelry wholesale, here’s why understanding diamond testers is critical:

• Avoid Misrepresentation: Mislabeling moissanite as diamond can lead to legal and ethical issues.

• Customer Trust: Today’s buyers are well-informed. Offering transparency about gemstone identity builds credibility.

• Inventory Accuracy: Proper testing ensures your catalog correctly reflects whether items are diamond, moissanite, or other gemstones.

For retailers, investing in a combined diamond & moissanite tester is a small cost compared to the potential risks of misidentification.

Common Myths About Moissanite and Diamond Testers

• Myth 1: “If it passes a diamond tester, it must be a diamond.”
  ❌ False. Moissanite also passes many diamond testers.

• Myth 2: “Moissanite is just a fake diamond.”
  ❌ Incorrect. Moissanite is a real gemstone with unique brilliance, fire, and durability.

• Myth 3: “Only labs can tell moissanite from diamond.”
  ❌ Not true. Skilled jewelers with the right tools can usually identify them without lab testing.

   

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Choosing the Right Tester for Your Business

If you handle moissanite wholesale jewelry, look for these features in a tester:

• Dual-probe (thermal + electrical conductivity)

• Fast detection response time

• Ability to test mounted stones

• Calibration for different gemstone sizes

Popular professional models include Presidium Multi Tester III and GemOro Testerossa.

Final Thoughts: Can a Diamond Tester Test Moissanite?

The answer is both yes and no. A basic thermal diamond tester will almost always mistake moissanite for diamond. Only advanced testers with electrical conductivity functions can accurately distinguish between the two.

As someone who has tested hundreds of stones, I recommend jewelers and wholesale buyers treat diamond testers as just one tool in a broader gem identification toolkit. Relying solely on them is risky, especially in today’s market where moissanite is not only common but also highly sought-after for its beauty and value.

At Moissanite Jewelry Wholesale, we pride ourselves on offering full transparency in gemstone identity—because the more educated our customers are, the more they appreciate the brilliance of moissanite on its own terms.

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