Short answer: Yes. Moissanite passes most standard thermal diamond testers because it conducts heat almost as well as diamond. A multi-tester, which also measures electrical conductivity, can tell the two stones apart. So can a trained jeweler with a 10x loupe.
If you own or are thinking about buying moissanite rings or other moissanite jewelry, this guide explains what happens at the jeweler's counter and why. It also covers how moissanite compares with natural and lab-grown diamonds.
Table of Contents
- Quick answer: does moissanite pass a diamond tester?
- How diamond testers work
- What happens on a standard thermal tester
- Can a multi-tester detect moissanite?
- Moissanite vs natural vs lab-grown diamond on testers
- Other ways jewelers tell moissanite from diamond
- Why people still choose moissanite
- FAQs
Quick Answer: Does Moissanite Pass a Diamond Tester?
On a basic thermal tester, yes. The tester will usually beep and show "diamond" when it touches moissanite.
On a multi-tester, no. Most modern jewelers use multi-testers, and these will flag the stone as moissanite. That is not a flaw in moissanite. It is a different gemstone with its own chemistry, and a good tester is designed to recognize it.
How Do Diamond Testers Work?
There are two main types of handheld tester used in the jewelry trade:
- Thermal conductivity testers: These measure how fast heat moves through the stone. Diamond is one of the best heat conductors of any material. Moissanite (silicon carbide) is also very good at moving heat, so a thermal tester alone often cannot separate the two.
- Electrical conductivity testers (multi-testers): These add a second check. Most diamonds are electrical insulators, while moissanite conducts a small amount of electricity. A multi-tester runs both checks and shows a separate "moissanite" reading.
What Happens When You Test Moissanite on a Standard Thermal Tester?
Say you test a moissanite engagement ring or a moissanite tennis bracelet with a basic thermal pen:
- The result: The tester lights up in the "diamond" zone and usually beeps.
- Why: The probe only reads heat flow. Both stones pull heat away from the probe tip quickly, so the reading looks the same.
This is why thermal-only testers are now seen as unreliable for telling diamond from moissanite. Most professional jewelers have moved to multi-testers.
Can a Multi-Tester Detect Moissanite?
Yes. A multi-tester checks heat first, then electrical conductivity. Moissanite conducts electricity slightly, so the tester shows a moissanite reading, often with a different light or sound.
One expert detail: some lab-grown diamonds made by the HPHT method contain traces of boron, which makes them conduct electricity. These rare stones can show up as "moissanite" on a multi-tester even though they are real diamonds. This is one reason gem labs do not rely on handheld testers alone for a final identification.
Moissanite vs Natural Diamond vs Lab-Grown Diamond on Testers
| Feature | Natural Diamond | Lab-Grown Diamond | Moissanite |
|---|---|---|---|
| Origin | Mined from the earth | Grown in a lab | Created in a lab |
| Material | Carbon (C) | Carbon (C) | Silicon carbide (SiC) |
| Thermal tester reading | Diamond | Diamond | Diamond |
| Multi-tester reading | Diamond | Diamond (rare boron-rich stones may read moissanite) | Moissanite |
| Refraction | Single | Single | Double |
| Hardness (Mohs) | 10 | 10 | 9.25 |
| Refractive index | 2.42 | 2.42 | 2.65 to 2.69 |
| Fire (dispersion) | 0.044 | 0.044 | 0.104 |
Want the full picture on moissanite set in silver? Read our guide: Moissanite and 925 Sterling Silver Jewelry: Why It's a Smart Choice.
Other Ways Jewelers Tell Moissanite From Diamond
- Double refraction under a loupe: Moissanite is doubly refractive. Looking through the stone at an angle, a jeweler can often see the back facet edges doubled. Diamond shows single, crisp facet edges.
- Rainbow fire: Moissanite has more than twice the dispersion of diamond. In bright sunlight it throws more colored flashes, which a trained eye may notice.
- Weight: Moissanite is lighter than diamond, so a moissanite stone of the same size weighs less.
- Lab report: For a definite answer, a gem lab such as the Gemological Institute of America (GIA) uses advanced equipment, not handheld testers.
Why People Still Choose Moissanite
A multi-tester can identify it, but moissanite remains one of the most popular gemstones for fine jewelry. Here's why:
- Brilliance and fire: Its higher refractive index (2.65 vs 2.42 for diamond) means strong sparkle and lots of colorful fire.
- Everyday durability: At 9.25 on the Mohs scale, it is harder than sapphire and ruby, and resists scratches well enough for daily rings and bracelets.
- Lab-created: No mining is needed to produce the stone.
- Value: You can choose a larger, clean-looking stone for far less than a mined diamond of the same size.
Browse moissanite pieces set in 925 sterling silver and solid gold:
- Men's moissanite and lab-grown diamond rings
- Women's rings
- Tennis bracelets and tennis chains
- Iced-out Cuban bracelets, including The Signature Cuban Bracelet (10mm)
- VVS moissanite custom nameplate pendants
Frequently Asked Questions
Does moissanite pass a diamond tester pen?
Most basic thermal tester pens will read moissanite as diamond. Multi-testers that also check electrical conductivity will identify it as moissanite.
Can a jeweler tell if my ring is moissanite?
Yes. A jeweler with a multi-tester or a 10x loupe can usually identify moissanite quickly, mainly from its electrical reading and double refraction.
Does a lab-grown diamond pass a diamond tester?
Yes. Lab-grown diamonds are real diamonds with the same carbon structure, so they pass both thermal and multi-testers. A few boron-rich HPHT stones may read as moissanite on a multi-tester.
Will my moissanite get cloudy over time?
No. Unlike cubic zirconia, moissanite does not turn cloudy or yellow with age. Any dullness is usually lotion or oil buildup. Clean it with warm water, mild soap and a soft brush.
Is moissanite a fake diamond?
No. Moissanite is its own gemstone, silicon carbide. It is used as a diamond alternative because it looks similar, but it has different optical and physical properties.
Can I wear moissanite jewelry every day?
Yes. With a hardness of 9.25, moissanite is well suited to daily-wear rings, earrings and bracelets in both silver and gold settings.
About the Author
Written by the Heero Gems team. We design and craft moissanite and lab-grown diamond jewelry in 925 sterling silver and 9K to 18K gold. We write these guides to answer the questions our customers ask most, so you can buy with confidence. Have a question? Contact us or explore the full collection.
