How to Spot Fake Moissanite: 7 Tests Every Buyer Should Know

The moissanite market has grown fast enough that it has attracted sellers who are not selling what they claim to be selling. Glass imitations, low-grade cubic zirconia, and synthetic stones of various kinds are sometimes marketed as moissanite — particularly at very low price points, and particularly from sellers who don't provide independent certification. If you've purchased moissanite and want to verify that it's genuine, or if you're considering a purchase and want to know how to protect yourself, this guide gives you seven practical tests that will tell you what you need to know.

Why Verification Matters

Genuine moissanite — silicon carbide (SiC) — has specific, measurable optical and physical properties that distinguish it from every other gemstone and from every imitation. These properties are not easy to fake, and they can be verified through a combination of certificate checks, visual inspection, and simple physical tests. The seven tests in this guide range from the simplest (checking the certificate) to the most definitive (professional gemological testing), and together they give you a complete picture of whether your stone is genuine.

Test 1: Verify the GRA Certificate

The first and most important test is the simplest: check the GRA certificate. Every genuine moissanite from a reputable seller comes with a GRA (Gemological Research Association) certificate that independently verifies the stone's identity and grade. The certificate includes a unique number that can be verified through GRA's online verification system.

Go to GRA's website, enter the certificate number, and confirm that the certificate is genuine and that the grades match what's stated on the certificate in your possession. If the certificate number doesn't appear in the system, or if the grades don't match, the certificate may be fraudulent.

If your stone didn't come with a GRA certificate, that is itself a significant red flag. A reputable moissanite seller provides a GRA certificate with every stone. For a complete explanation of GRA certification, see our article on GRA certification explained.

Test 2: The Scratch Test

Moissanite scores 9.25 on the Mohs hardness scale — significantly harder than glass (5.5), cubic zirconia (8–8.5), and most other imitations. A genuine moissanite stone will scratch glass easily; glass and most imitations will not scratch moissanite.

To perform the scratch test: take a piece of ordinary glass (a glass plate or a glass tile works well) and attempt to scratch it with the pointed tip or edge of the stone. A genuine moissanite will leave a clear scratch in the glass. If the stone doesn't scratch the glass, or if the stone itself shows a scratch from the contact, it is not genuine moissanite.

Note: this test should be performed carefully to avoid damaging the stone's setting. If you're uncertain, have a jeweler perform the test for you.

Test 3: The Loupe Inspection

Moissanite has a specific internal structure that is visible under magnification. Under a 10x loupe, genuine moissanite may show needle-like inclusions that run parallel to the crystal's growth direction — a characteristic feature of silicon carbide crystals. These inclusions are not defects; they are a natural result of the crystal growth process and are present even in VVS1 stones (though they are extremely difficult to see at this clarity grade).

Glass imitations have no internal structure — they appear completely uniform under magnification. Cubic zirconia may show gas bubbles or other inclusions that are different in character from moissanite's needle-like inclusions. A jeweler with experience in moissanite can identify the stone's internal structure under magnification with confidence.

Test 4: The Double Refraction Test

Moissanite is doubly refractive — it splits light into two rays as it passes through the crystal, a property called birefringence. This means that when you look through a moissanite stone at a straight line or a point of light, you will see a slight doubling of the image. Diamond is singly refractive and does not show this doubling. Glass and cubic zirconia are also singly refractive.

To perform this test: hold the stone face-down over a piece of paper with a printed line, or look through the stone at a distant point of light. If you see a slight doubling of the line or the light point, the stone is doubly refractive — consistent with moissanite. If the image is single and clear, the stone may be diamond, glass, or cubic zirconia.

Note: this test requires some practice to interpret correctly, and the doubling effect can be subtle in well-cut stones. It is most useful as a confirmatory test rather than a definitive one.

Test 5: The Thermal Conductivity Test

Moissanite has very high thermal conductivity — it conducts heat efficiently, which means it feels cool to the touch and warms quickly when held. This property is similar to diamond and different from glass and cubic zirconia, which are thermal insulators.

A thermal conductivity tester — a device used by jewelers to distinguish diamond from imitations — will register moissanite as a conductor, similar to diamond. This is why moissanite passes the standard diamond tester: both stones conduct heat efficiently. A more sophisticated tester that measures electrical conductivity can distinguish moissanite from diamond, because moissanite is a semiconductor while diamond is an electrical insulator.

For more on how moissanite performs on diamond testers, see our article on what happens when a jeweler tests your moissanite.

Test 6: The Fire and Brilliance Test

Genuine moissanite has a dispersion rate of 0.104 — the highest of any fine jewelry gemstone. In direct light, it produces vivid, clearly defined rainbow flashes (fire) that are significantly more colorful than diamond and dramatically more colorful than glass or cubic zirconia. If your stone produces vivid rainbow fire in direct sunlight or bright artificial light, this is consistent with genuine moissanite.

Glass produces very little fire — it appears relatively flat and lifeless in direct light. Cubic zirconia produces some fire, but less than moissanite and with a different character. If your stone appears dull or flat in direct light, it is unlikely to be genuine moissanite.

For a complete explanation of moissanite's fire and how it appears in different lighting conditions, see our article on moissanite's rainbow effect explained.

Test 7: Professional Gemological Testing

The most definitive test is professional gemological testing by a qualified gemologist with access to a moissanite tester — a device that measures electrical conductivity and can definitively distinguish moissanite from diamond, glass, cubic zirconia, and other imitations. This test is available at most jewelry stores and gemological laboratories, typically for a small fee.

If you have any doubt about the authenticity of your stone after performing the other tests in this guide, professional gemological testing is the definitive answer. A qualified gemologist can also inspect the stone's internal structure under magnification and compare its optical properties against known moissanite standards.

What to Do If Your Stone Fails the Tests

If your stone fails one or more of these tests, contact the seller immediately. A reputable seller will take the concern seriously, offer to have the stone independently tested, and provide a replacement or refund if the stone is not genuine moissanite. A seller who dismisses your concern or makes it difficult to resolve is a seller who should not have your business.

At Moissanite Shine, every stone we sell is GRA certified and backed by our Lifetime Gemstone Warranty. If you have any concern about the authenticity of a stone you purchased from us, our team is available to assist — and we will make it right. For guidance on buying moissanite safely from any seller, see our article on how to buy moissanite online safely.