Effective Methods To Accurately Test Moissanite Using A Diamond Tester

Misidentifying gemstones is a common challenge in jewelry retail, appraisal, and personal ownership. Moissanite, with its striking visual similarity to diamond, often triggers false positives on standard diamond testers. While this resemblance benefits consumers seeking an affordable, durable alternative, it also creates confusion when verifying authenticity. Understanding how to use a diamond tester effectively—especially when distinguishing between moissanite and diamond—is essential for accuracy. This guide outlines proven methods, tools, and techniques to ensure precise results when testing moissanite.

Understanding How Diamond Testers Work

Diamond testers measure thermal or electrical conductivity to determine whether a stone is likely a diamond. Traditional models rely on thermal conductivity: diamonds dissipate heat rapidly, which the device detects. However, moissanite shares high thermal conductivity with diamond, leading many older testers to misidentify moissanite as diamond.

Modern testers incorporate electrical conductivity testing because moissanite is electrically conductive—unlike diamond. Dual-mode testers (thermal + electrical) are far more reliable for differentiating between the two stones. When only thermal testing is used, moissanite frequently passes as diamond, creating a critical flaw in assessment accuracy.

“Over 70% of consumer-grade diamond testers fail to distinguish moissanite without dual-sensor technology.” — Dr. Alan Reed, Gemological Instrumentation Specialist

Tip: Always verify that your diamond tester has both thermal and electrical conductivity sensors before relying on its results.

Step-by-Step Guide to Accurately Test Moissanite

To avoid misidentification, follow this systematic process when using a diamond tester on a suspected moissanite stone.

1. Power on and calibrate the tester – Allow the device to warm up and confirm it’s functioning properly using the included calibration tool or reference stone.
2. Clean the stone thoroughly – Residue, oils, or dirt can interfere with conductivity readings. Use a soft cloth and mild soapy water, then dry completely.
3. Position the probe correctly – Place the tip perpendicular to the crown of the stone, avoiding settings or metal contacts that could skew results.
4. Observe initial reading – If the tester indicates “diamond,” do not conclude yet. Moissanite often registers as diamond on thermal-only devices.
5. Check for double refraction (visual inspection) – Look through the table of the stone with a loupe. Moissanite displays doubled facet junctions due to birefringence; diamonds do not.
6. Use a dual-mode tester – If available, switch to electrical mode. A positive electrical conductivity result strongly suggests moissanite.
7. Confirm with additional tools – Cross-check results using a jeweler’s loupe, refractometer, or professional lab services if uncertainty remains.

Comparison: Tester Types and Their Accuracy with Moissanite

Tester Type	Thermal Conductivity	Electrical Conductivity	Reliability with Moissanite	Recommended?
Basic Thermal Tester	Yes	No	Low – Often misreads moissanite as diamond	No
Dual-Sensor Tester	Yes	Yes	High – Can differentiate based on electrical response	Yes
Digital Multi-Gem Tester	Yes	Yes	Very High – Identifies diamond, moissanite, CZ, and others	Strongly Recommended
UV Fluorescence Tool	No	No	Moderate – Some moissanites fluoresce blue under UV	Supportive Only

Tip: Upgrade to a digital multi-gem tester if you regularly handle loose stones or appraise jewelry—models like the Presidium GemMate II or GIA-tested units offer superior reliability.

Real-World Scenario: The Misidentified Engagement Ring

A customer brought a vintage-style engagement ring to a local jeweler, believing it contained a 1-carat diamond. The store used a basic thermal diamond tester, which confirmed “diamond.” Satisfied, the customer proceeded with insurance valuation. Months later, during a routine appraisal update, a certified gemologist used a dual-mode tester and observed electrical conductivity. Further examination under magnification revealed double facet lines—a hallmark of moissanite.

The ring was indeed set with a high-quality moissanite. While not fraudulent, the initial oversight led to over-insurance and inaccurate documentation. This case underscores the importance of using advanced testers and not relying solely on thermal results—even in professional environments.

Best Practices and Common Mistakes

Avoid these frequent errors when testing moissanite:

• Using outdated or single-mode testers – These lack the capability to detect electrical properties unique to moissanite.
• Testing through metal settings – Contact with prongs or bezels can distort readings. Ensure direct contact with the girdle or crown.
• Ignoring environmental factors – Extreme temperatures or humidity can affect sensor performance. Test in stable conditions.
• Skipping visual inspection – Birefringence is a definitive clue. Always examine the stone with at least a 10x loupe.
• Assuming all “diamond-like” stones are fake – Moissanite is a legitimate gemstone with value. Proper identification respects its place in the market.

“Technology should support judgment, not replace it. Combine instrument data with observational skills.” — Lila Chen, Certified Gemologist, AGS

FAQ: Testing Moissanite with Diamond Testers

Can a diamond tester tell the difference between moissanite and diamond?

Only if it measures electrical conductivity. Most modern dual-mode testers can distinguish between the two by detecting moissanite’s electrical conductivity, which diamond lacks.

Why does my diamond tester say my moissanite is a diamond?

This happens with thermal-only testers. Moissanite conducts heat similarly to diamond, so older or basic models cannot differentiate them. You need a dual-mode or multi-gem tester for accurate results.

Is moissanite considered a fake diamond?

No. Moissanite is a distinct gemstone with its own chemical composition (silicon carbide). It’s not “fake” but rather a diamond alternative with comparable brilliance and durability at a lower price point.

Essential Checklist for Accurate Moissanite Testing

1. ✔️ Use a dual-mode (thermal + electrical) diamond tester
2. ✔️ Clean the stone before testing
3. ✔️ Avoid contact with metal settings during probing
4. ✔️ Inspect for double refraction using a 10x loupe
5. ✔️ Confirm results with a second method if uncertain
6. ✔️ Record findings, especially for insurance or resale purposes
7. ✔️ Store and maintain your tester according to manufacturer guidelines

Conclusion: Precision Matters in Gemstone Identification

Accurately identifying moissanite isn’t about discrediting its value—it’s about ensuring transparency, proper valuation, and informed decision-making. Whether you're a jeweler, appraiser, or consumer, relying on outdated tools risks costly misunderstandings. By using dual-sensor testers, combining technological results with visual analysis, and staying informed about gemstone properties, you protect both financial interests and trust in transactions.

💬 Have you encountered a misidentified moissanite? Share your experience or questions below. Your insights could help others avoid the same pitfalls.