Do Moissanite & Lab Diamonds Pass a Diamond Tester?
A common question with a surprising answer. Here's how diamond testers actually work.
Diamond testers are handy little tools — but they're often misunderstood. Whether a stone “passes” depends on what the tester measures and what the stone is.
Lab grown diamonds: yes, they pass
Because a lab grown diamond is chemically identical to a mined one, it conducts heat exactly the same way — so it passes a standard diamond tester every time. That's expected: it is a diamond.
Moissanite: it depends on the tester
Older thermal-only testers measure heat conductivity, and moissanite can read as “diamond” on those. But modern moissanite/diamond combo testers also measure electrical conductivity, which easily tells moissanite apart. So on a good dual tester, moissanite is correctly identified as moissanite.
Why this matters
It's a reminder that a basic tester isn't proof of a mined diamond — it only checks heat conductivity. For certainty about any stone, rely on a grading report from a lab like IGI or GIA. More on that in Certification: GIA vs IGI.
FAQs
Do lab grown diamonds pass a diamond tester?
Yes, always — they're real diamonds with identical heat conductivity.
Does moissanite pass a diamond tester?
On basic thermal testers it can read as diamond; modern combo testers correctly identify it as moissanite.
What's the most reliable way to confirm a stone?
A grading report from a reputable lab such as IGI or GIA.
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