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Standard thermal conductivity diamond testers can read moissanite as diamond due to overlapping thermal properties. Specialist moissanite-specific testers or spectrographic equipment accurately identifies moissanite. This guide explains every test and its results honestly.
Whether moissanite passes a diamond tester depends on the type of tester used. Standard thermal conductivity diamond testers — the most common type used in jewellery retail — can read moissanite as diamond because moissanite has thermal conductivity properties that overlap with diamond in some measurement ranges.
Moissanite-specific testers add an additional measurement that distinguishes moissanite from diamond accurately. IGI and other gemological laboratories use spectrographic equipment that identifies moissanite definitively from its crystal structure and double refraction.
| Tester Type | Result with Moissanite | Explanation |
|---|---|---|
| Standard thermal conductivity tester | May read as diamond | Moissanite thermal conductivity overlaps with diamond in some measurement ranges |
| Multi-tester (thermal + electrical) | Usually identifies as moissanite | Electrical conductivity test distinguishes most moissanite from diamond |
| Dedicated moissanite tester | Correctly identifies as moissanite | Specifically designed to separate moissanite from diamond |
| IGI / gemological lab spectrograph | Definitively identifies as moissanite | Crystal structure, double refraction and spectral signature are definitive |
Standard diamond testers measure thermal conductivity — how quickly heat moves through the material. Diamond has very high thermal conductivity. Most gemstone simulants (cubic zirconia, glass, white sapphire) have much lower thermal conductivity and test clearly as not-diamond.
Moissanite is unusual in that its thermal conductivity, at some measurement conditions, overlaps with diamond. This causes some thermal conductivity testers to read moissanite as diamond. It is not that moissanite is trying to pass as diamond — it is that the measurement technique used by standard testers does not clearly separate the two materials.
Several methods accurately identify moissanite.
Book a free online consultation. Yash Chandpara explains the differences between moissanite and diamond and how each is identified.
