Quick answer
Yes, moissanite does pass most standard diamond testers. The common handheld tester measures how fast a stone carries heat away, and moissanite conducts heat very much like diamond, so the tester reads "diamond." A multi-tester that also measures electrical conductivity will tell the two apart in seconds.
That is the short answer. Here is what it means in practice, and why a tester beep should never be the reason you buy moissanite.
Key takeaways
- Thermal testers read moissanite as diamond, because both carry heat away fast.
- Multi-testers add an electrical conductivity check and flag moissanite in seconds.
- A 10x loupe shows doubled facet lines, and a scale shows moissanite is about 10% lighter for its size.
- Buy moissanite for its look, its 9.25 Mohs hardness and its price, never to pass it off as diamond.
Why does moissanite pass a standard diamond tester?
Most pocket testers are thermal testers. A heated metal tip touches the stone and measures how quickly the heat moves away. Diamond pulls heat away fast. Glass and cubic zirconia don't, so they fail.
Moissanite is silicon carbide, and it handles heat in a way very close to diamond. A thermal-only tester can't see the difference, so it lights up "diamond." That is why jewelers stopped relying on these testers alone once moissanite showed up on the market.
How a multi-tester tells them apart
Many jewelers now use a multi-tester. It runs the heat test first, then checks electrical conductivity. On that second reading, moissanite and diamond behave differently, and the tester flags the stone as moissanite.
So if someone tells you their stone "passed the diamond test," the right follow-up question is simple: which tester?
| Test | What it checks | Result on moissanite |
|---|---|---|
| Standard thermal tester | Heat conductivity | Usually reads as diamond |
| Multi-tester | Heat and electrical conductivity | Identified as moissanite |
| 10x loupe | How light travels through the stone | Doubled facet lines at an angle |
| Scale | Weight for a given size | About 10% lighter than diamond |
How the four common checks read a moissanite.
Other ways a jeweler spots moissanite
Doubled facet lines
Moissanite is doubly refractive. Light splits in two as it passes through the stone. Look through a 10x loupe at an angle, not straight down through the top, and the back facet edges look doubled, like a slightly ghosted photo. You won't see that doubling in a diamond.
More rainbow fire
Dispersion is the measure of how much a stone splits white light into color. Moissanite sits at 0.104. Diamond sits at 0.044. That is more than twice the rainbow flash.
In sunlight or under a spotlight, you can see it. Some people love that colorful sparkle. Others prefer the cooler, whiter sparkle of diamond. Neither is wrong, but it's worth knowing before you buy.
Weight
Moissanite is about 10% lighter than diamond. That is why moissanite is sold by DEW, diamond equivalent weight. A "1 carat" round moissanite is the size of a 1 carat diamond, about 6.5mm across, even though it weighs a little less on a scale.
Good to know
A 6.5 mm round moissanite is about 1 ct DEW, yet it weighs about 0.88 ct. Moissanite's density is about 3.21 g/cm3 against 3.52 for diamond, and a jeweler's scale picks up that gap right away.
Should you pass moissanite off as diamond?
No. And you don't need to.
Moissanite is its own gemstone with its own strengths. Any trained jeweler with a multi-tester or a loupe will identify it, and the story you tell about a piece matters. Wear it as moissanite, proudly. At Daellia, every stone is sold as exactly what it is.
For the full background on the stone, our moissanite guide is a good next read.
What moissanite does well
- Hardness of 9.25 on the Mohs scale. Diamond is 10, cubic zirconia is 8 to 8.5. Moissanite holds up to everyday wear on rings and bracelets.
- Brilliance. Its refractive index is 2.65 to 2.69, higher than diamond at 2.42 and cubic zirconia at 2.15 to 2.18. In practice, that means a lot of light coming back to your eye.
- It stays clear. Moissanite does not cloud or fade over time.
- Price. It's lab-grown, so a stone the size of a 1 carat diamond costs far less than the mined version.
Moissanite vs cubic zirconia on a tester
Cubic zirconia is the stone most people confuse with moissanite, and a thermal tester won't mistake it for diamond. CZ is also softer, so it scratches more easily, and it returns less light. If a stone reads as diamond on a basic thermal tester, it is not CZ.
Want the full side-by-side on materials, hardness and fire? Read is moissanite real, and why it costs less.
A tester beep is not a reason to buy. How the stone looks on you is.The Daellia Journal
What Daellia moissanite is
Our white moissanite is D color, the top of the color scale, and VVS1 clarity, which means inclusions are extremely hard to find even under magnification. We set it in 925 sterling silver plated with rhodium or 18K gold, and in 14K gold filled. All our metals are nickel- and lead-free.
A few pieces people start with:
- Véga Solitaire Studs, the everyday pair.
- Sirius Solitaire Ring, a clean single stone.
- Our moissanite engagement rings, for the bigger question.
Where people start
The bottom line
A standard thermal diamond tester will usually call moissanite a diamond. A multi-tester will not. A loupe and a scale give it away too.
Buy moissanite because you like how it looks, how hard it is and what it costs. That is reason enough. Still have questions? Check our FAQ. And to keep your stone bright for years, read does moissanite get cloudy.
See it for yourself.
Shop our best-selling moissanite pieces, with free tracked shipping on every US order.
Shop best sellersFrequently asked questions
Can a jeweler tell moissanite from a diamond?
Yes, and it usually takes a minute. A multi-tester flags moissanite through its electrical conductivity, and a 10x loupe shows doubled facet lines when you look through the stone at an angle. A scale helps too: for the same size, moissanite weighs about 10% less than diamond. A basic thermal tester is the one tool that gets fooled.
Do lab-grown diamonds pass a diamond tester?
Yes. Lab-grown diamonds are real diamond, pure carbon with the same chemical and physical properties as mined stones, so a thermal tester reads them as diamond. A tester can't tell you whether a diamond was grown or mined; gem labs use spectroscopy for that. Moissanite is a different material that simply handles heat in a similar way.
Does cubic zirconia pass a diamond tester?
No. Cubic zirconia is a thermal insulator, like almost every other diamond simulant, so a thermal tester reads it as "not diamond" right away. That makes CZ the easiest stone to rule out. Moissanite is the exception because it carries heat much like diamond, which is why a thermal-only tester can't separate those two.
Can a real diamond ever test as moissanite?
It can happen with blue diamonds. The boron that gives natural blue diamonds their color also lets them conduct electricity, and electrical conductivity is exactly what a multi-tester uses to flag moissanite. For colorless diamonds this isn't an issue. If a reading looks odd, a gem lab can confirm the stone with magnification and spectroscopy.
Can moissanite be sold as a diamond?
No. The FTC's Jewelry Guides treat it as deceptive to call a stone a diamond unless it really is one, and lab-created gems must be clearly described as laboratory-created, laboratory-grown or synthetic. Moissanite should always be sold under its own name. If a listing blurs that line, shop somewhere else.
Keep reading
Written by the Daellia Journal team, Paris. We write about moissanite, metals and the stories behind fine jewelry so you can buy with confidence. Read our moissanite guide or our story.
