Does Moissanite Pass a Diamond Tester? The Honest Answer

Short answer: yes - moissanite passes a standard diamond tester, but that does not mean it is a diamond, and a jeweler with the right tool can tell the two apart in seconds. Here is exactly why that happens and what it means when you are buying moissanite jewelry.

The quick answer

Most handheld “diamond testers” are actually thermal conductivity testers. They measure how quickly a stone moves heat. Diamond conducts heat extremely well - and so does moissanite. Because their thermal conductivity is so similar, a basic thermal tester will read “diamond” (or “pass”) for a moissanite stone. So if someone touches a classic diamond pen to your moissanite, it will read as diamond.

How a diamond tester actually works

A traditional diamond tester heats a tiny metal tip and presses it against the stone. Diamonds pull heat away from the tip very fast; glass, cubic zirconia and most imitations do not. The tester uses that difference to say “diamond” or “not diamond.” The catch is that moissanite is nearly as good at conducting heat as diamond, so it fools any tester that only measures heat.

So how do jewelers tell moissanite and diamond apart?

Newer testers - often called moissanite testers or dual testers - add a second measurement: electrical conductivity. Diamond does not conduct electricity, but moissanite does. A dual tester checks heat and electricity, so it can correctly separate the two. Jewelers also use magnification (moissanite shows a slight “doubling” of the facet edges) to confirm. In short: a cheap thermal pen says “diamond,” but a proper moissanite or dual tester says “moissanite.”

Does passing the test mean moissanite is “fake”?

No. Moissanite is a real gemstone (silicon carbide) - it simply is not a diamond. It was first discovered in a meteor crater and is now created in controlled lab conditions. It has its own brilliance - actually more colored “fire” than diamond - and a hardness of about 9.25 on the Mohs scale, second only to diamond at 10. It is a genuine stone, not a cheap imitation like cubic zirconia or glass, which is exactly why it behaves like diamond on a heat tester.

What this means when you are buying moissanite

For everyday wear - cluster earrings, tennis chains, tennis bracelets and rings - moissanite gives you diamond-level sparkle and durability at a fraction of the cost. Because it passes a basic diamond tester, it also reads as diamond to most people who casually check. We are always upfront that our stones are lab-created moissanite set in real .925 sterling silver, so you know exactly what you are wearing.

How to test your own moissanite at home

• Thermal pen: it will read “diamond” - expected, not a defect.
• Dual / moissanite tester: the accurate tool; it will correctly identify moissanite.
• The sparkle test: moissanite throws more rainbow “fire” than diamond, especially in bright light.
• Skip the viral fog and water hacks - they are not reliable; use a proper tester.

Frequently asked questions

Does moissanite pass a diamond tester? Yes - a standard thermal diamond tester reads moissanite as diamond because their heat conductivity is nearly identical.

Will a jeweler know it is moissanite? Yes, if they use a moissanite or dual tester, or magnification. That is normal and expected.

Is moissanite a real stone? Yes - it is silicon carbide, a genuine gemstone that is lab-created today, not an imitation.

Is moissanite as hard as diamond? Almost - about 9.25 versus diamond’s 10 on the Mohs scale, which makes it excellent for daily wear.

Want the sparkle without the diamond markup? Explore our full moissanite collection in .925 sterling silver, with free insured shipping and 30-day returns.