Short answer: yes and no. Moissanite passes a basic thermal diamond tester, because it conducts heat almost as well as a diamond, so the older pen style testers read it as diamond. It does not pass a modern tester that also checks electrical conductivity: moissanite carries a small charge and diamond does not, so any combination tester names it as moissanite in seconds. Most jewelers now use that combination type.
Why does moissanite pass a heat based tester?
A traditional diamond tester measures how quickly a stone moves heat away from its tip. Diamond is one of the best heat conductors of any material, and moissanite sits right behind it, so a heat only tester cannot separate the two and shows a diamond reading for both. This is where the idea that moissanite fools testers comes from, and it was true for the simple testers sold years ago.
Why does it fail a modern tester?
Newer testers add a second measurement for electrical conductivity. Moissanite conducts a little electricity; diamond conducts almost none. A tester with a moissanite setting runs both checks and tells the two stones apart instantly. These combination testers are inexpensive and standard at jewelry counters, so a professional will always know which stone is in front of them.
| Tester type | Reads moissanite as | Reads diamond as |
|---|---|---|
| Thermal only (older pen style) | Diamond (passes) | Diamond |
| Electrical or moissanite mode | Moissanite (flagged) | Diamond |
| Combination (heat plus electrical) | Moissanite (flagged) | Diamond |
How can I tell moissanite from a diamond myself?
You rarely need a machine. Hold the stone under a bright light: moissanite has a higher refractive index than diamond, so it throws more rainbow colored flashes, an effect some people call the disco ball look. Tilt it and view the top with a loupe, and the back facet edges can appear doubled, because moissanite is doubly refractive and diamond is not. The price is the plainest clue of all, since a moissanite of the same size costs a small fraction of a mined diamond.
Does passing a tester mean moissanite is fake?
No. Moissanite is a real gemstone made of silicon carbide, grown in a lab rather than mined from the ground. It is not an imitation like glass or cubic zirconia; it is a stone in its own right that happens to resemble diamond. At 9.25 on the Mohs hardness scale it is the hardest stone used in fine jewelry after diamond itself, so it shrugs off everyday scratches and keeps its clarity and color for life. Passing a heat tester simply reflects how well it moves heat, which is one of the qualities that make it brilliant and hard wearing, not a flaw.
Shop moissanite at Fashorio
Every Fashorio moissanite ring is set in 925 sterling silver and cut for maximum brilliance. Browse the full ring collection or the wider jewelry edit, and use our ring size guide to get the fit right the first time. To weigh moissanite against a mined stone, read is moissanite a good alternative to a diamond.
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