A post on r/Moissanite gets 400 upvotes and dozens of replies. The story: someone bought a "moissanite" ring from an online seller, took it to a jeweler, and found out it was CZ. The comments fill with people who've had similar suspicions about stones they own, and with others sharing how they eventually confirmed theirs was real.
It's a legitimate concern. The moissanite market includes sellers who knowingly or unknowingly substitute cubic zirconia — a much cheaper and less durable stone — for moissanite. And because both stones are clear, sparkly, and not diamond, the swap can go undetected for a long time.
Here's how to actually tell them apart, ranked from most reliable to most accessible.
Method 1: Dedicated Moissanite/Diamond Tester (Most Reliable Electronic Test)
The most reliable consumer-accessible test is a dedicated electronic tester that distinguishes between moissanite, diamond, and CZ. These devices — sometimes called "multi-stone testers" or "diamond/moissanite testers" — work differently from the standard thermal probes used in most jewelry stores.
A standard thermal probe tests heat conductivity. Diamonds conduct heat rapidly. CZ conducts heat slowly. For decades, this was sufficient: you tested the stone, it either read as diamond or it didn't, and "not diamond" meant CZ or glass.
Moissanite disrupted this. Moissanite conducts heat similarly to diamond, so some older thermal probes read moissanite as "diamond." Sellers of fake moissanite (actual CZ or glass sold as moissanite) rely on buyers using only thermal probes.
A dedicated moissanite tester uses electrical conductivity in addition to thermal conductivity, or uses a combination of optical and thermal sensing, to specifically identify moissanite as a distinct category from both diamond and CZ. When used correctly, these testers will return one of three results: diamond, moissanite, or simulant (CZ/glass).
How to use: Touch the probe tip to the table or a large facet of the clean stone. Hold still until the device beeps or lights up. A reading of "moissanite" or "MOS" is a strong positive identification.
Limitations: Different tester brands have different accuracy levels. Some cheaper units are less reliable. Always use a tester from a reputable brand and test on a clean stone — oils, dirt, or moisture can interfere with readings. Some very small stones (under 3mm) are difficult to test accurately.
Method 2: Loupe Inspection for Double Refraction (Most Accessible Visual Test)
This is the test you can do yourself with a jeweler's loupe or even a macro lens on your phone, and it's highly reliable when done correctly.
Moissanite is doubly refractive. This means each ray of light entering the stone is split into two separate rays. When you look through the stone and focus on the facets on the opposite side (the pavilion facets), in moissanite you'll see each facet edge appears doubled — like a slight ghost or shadow alongside the primary line.
Cubic zirconia is singly refractive, like diamond. Facet edges appear as single, clean lines.
How to perform the test:
- Clean the stone thoroughly so the surface is clear.
- Hold a 10x jeweler's loupe close to your eye and look through the top of the stone (the table facet) down toward the bottom.
- Focus on the facets at the bottom of the stone (the pavilion).
- In moissanite, the facet edges will appear doubled — you'll see a distinct "shadow line" parallel to each facet edge.
- In CZ, the facet edges will appear as single clean lines.
This test works best with brilliant cuts where the pavilion facets are large and clear. It's harder to execute on very small stones or with very shallow cuts.
Important: This test requires a loupe of at least 10x magnification. You won't see the doubling clearly with the naked eye. If you don't have a loupe, many jewelers will let you use theirs if you explain what you're looking for.
Method 3: Fire Pattern Observation (Visual Comparison)
This test doesn't require equipment but does require knowing what to look for. It's useful as a supplement to the loupe test, not as a standalone.
Moissanite has a dispersion rating of 0.104 — more than twice diamond's 0.044 and significantly higher than CZ's 0.066. This means moissanite produces more colored fire (rainbow flashes) than CZ under the same lighting.
Under a bright light source, moissanite fire is distinctly colorful and intense. CZ fire exists but is more subdued. The difference is most visible when comparing side by side, but experienced eyes can often spot moissanite's fire level in isolation.
Practical application: Hold the stone under a direct light source (phone flashlight works well) and tilt it slowly. In moissanite, you'll see vivid, multi-colored flashes. In CZ, the flashes are present but notably less intense. If the stone produces almost no colored fire — just white or grey reflections — it may be glass or low-quality CZ.
This test is impressionistic and context-dependent. It's most useful as a "something seems off" signal that prompts you to do more rigorous testing.
Method 4: Specific Gravity / Weight (Lab Test)
Moissanite has a specific gravity of approximately 3.21. Cubic zirconia has a specific gravity of approximately 5.65 to 5.90. This means CZ is significantly heavier than moissanite for the same physical size.
This is the most conclusive non-electronic physical test, but it requires precise equipment: a lab-grade scale accurate to 0.001g and distilled water for hydrostatic weighing. It's not a test most consumers can perform at home, but gemological labs can do it quickly.
Practical note: The weight difference is noticeable by feel if you have stones of the same cut and carat weight to compare. A 1ct CZ will feel noticeably heavier than a 1ct moissanite. If you have another verified stone to compare, weighing both on a precise scale will reveal a significant difference if one is CZ.
Method 5: UV Fluorescence
Under long-wave UV light, moissanite typically shows orange or yellow fluorescence. CZ usually shows no fluorescence or a different color. Diamond fluorescence varies widely (most commonly blue, but also none, yellow, or orange).
How to test: Use a UV flashlight (long-wave, 365nm) in a dark room. Hold the light close to the stone and observe the color emitted.
Limitations: UV fluorescence is not a definitive test for moissanite because the response varies between stones and manufacturers. Some moissanite shows strong fluorescence; some shows weak or none. Some CZ shows fluorescence too. This test is best used as supporting evidence alongside other methods, not as a standalone identifier.
Method 6: GRA Certificate (Documentation Test)
The most straightforward proof of moissanite identity is documentation. GRA (Gemological Research Association) certificates are issued specifically for moissanite and state the stone's identity, color grade, clarity grade, and size.
If you bought from a legitimate moissanite seller, your stone should have come with a GRA certificate or equivalent documentation. This certificate has a unique ID that can be verified through GRA's registry.
What to do if you don't have a certificate: Reputable sellers will provide documentation on request. If the seller you bought from can't or won't provide documentation, that itself is a red flag.
What the certificate tells you: GRA certificates identify the stone as moissanite and specify DEF, GHI, or JK color grade. They don't authenticate the stone's current condition (they're issued at time of grading), but they establish what was sold.
Red Flags That Suggest You May Have CZ
Before even testing, certain seller and product characteristics are associated with higher risk of misrepresentation:
Unusually low price. Moissanite has real manufacturing costs. A 1ct round brilliant from a reputable seller typically ranges from $80 to $200+ depending on color grade and source. Prices significantly below this range — especially on unregulated platforms — are a red flag.
No certificate offered. Legitimate moissanite sellers include GRA or equivalent documentation. If a seller can't provide documentation and becomes evasive when asked, treat the stone with suspicion.
"Grade D" or "AAAAA" grade claims. These are not real moissanite grading standards. Real moissanite uses GRA's DEF / GHI / JK color grading. Marketing terms like "Grade D AAAAA moissanite" with no GRA documentation are often applied to CZ being sold as moissanite.
Inconsistent fire. If the stone produces less fire than expected for a moissanite of its size and cut, the dispersion may be lower than moissanite's — consistent with CZ.
Stone that has clouded or scratched. Moissanite rates 9.25 on the Mohs hardness scale and resists scratching under normal conditions. If a stone sold as moissanite has become scratched or cloudy within a few years of normal wear, it may be CZ (which is softer and degrades more easily).
What to Do If You Think Your Stone Is CZ
If the testing methods above suggest your stone is CZ rather than moissanite:
First, retest carefully. Make sure the loupe test was performed correctly (looking at pavilion facets through the table) and that the electronic tester is reliable and the stone was clean. A single inconclusive test isn't enough.
Get a gemologist assessment. An independent gemologist with proper equipment — including a dedicated moissanite/diamond tester and a refractometer — can give a definitive assessment, usually for a small fee. This is more reliable than any consumer-grade test.
Document your purchase. If you confirm the stone is CZ, gather your purchase records, any correspondence with the seller, and any documentation they provided. This is important for any dispute or refund claim.
Contact the seller. Legitimate sellers will take the situation seriously if you contact them with evidence. Sellers who ignore the issue or become hostile are more likely to be bad actors.
Report if appropriate. If you believe you were deliberately sold CZ as moissanite, consumer protection authorities and payment platform dispute processes exist for this purpose.
Frequently Asked Questions
Can I tell moissanite from CZ just by looking?
Not reliably without magnification. The fire difference is visible to a trained eye but subtle enough that casual observation isn't conclusive. The loupe test for double refraction is the most accessible reliable test that doesn't require electronic equipment.
Will a standard jewelry store diamond tester identify moissanite?
Standard thermal probes may read moissanite as "diamond" (because both conduct heat rapidly) rather than correctly identifying it as moissanite. They will typically identify CZ as "not diamond." A thermal probe result of "diamond" on a stone sold as moissanite is consistent with — but doesn't confirm — moissanite. You need a dedicated moissanite tester or a loupe inspection to confirm moissanite specifically.
Is there an at-home test that requires no equipment?
Fire pattern observation (Method 3) requires no equipment but is the least conclusive. The loupe inspection requires a 10x loupe, which is inexpensive (under $20 on most retail sites) and worth having. There's no fully equipment-free test that's reliably conclusive.
How much does a moissanite tester cost?
Consumer-grade combined diamond/moissanite testers typically cost $30 to $80. Professional-grade versions cost more. For regular buyers who purchase multiple moissanite pieces, owning one is practical. For a one-time verification, having a gemologist test the stone is usually more cost-effective.
Does moissanite ever test as CZ?
On a properly functioning dedicated moissanite tester, no — a genuine moissanite stone will not return a CZ reading. On a standard thermal probe, neither moissanite nor CZ will return a "diamond" reading consistently (moissanite sometimes reads as diamond on thermal probes). If a dedicated moissanite tester returns "simulant" or "CZ" on a stone sold as moissanite, the stone is almost certainly not moissanite.
The Bottom Line
The most reliable way to confirm moissanite identity is a combination of a dedicated electronic moissanite/diamond tester and a loupe inspection for double refraction. Either alone is strong evidence; both together is conclusive for most practical purposes. GRA documentation establishes what was sold at point of purchase.
If you're uncertain about a stone you own, a gemologist assessment is the most conclusive path — typically inexpensive and definitive. If you're buying moissanite, choose sellers who provide GRA certificates and have verifiable reputations.
Oglowa moissanite comes with GRA certification and is made from DEF color, VVS1 clarity silicon carbide — the real material, properly documented. Browse moissanite jewelry
