Why Lab-Grown Diamonds May Test as Moissanite

Lab-grown diamonds and moissanite are both popular alternatives to natural diamonds, and while they share some similarities, they have key differences that can lead to confusion in testing. This article explores the reasons why lab-grown diamonds might test as moissanite under certain conditions and how to accurately distinguish between the two.

Key Differences: Composition and Testing Methods

Lab-grown diamonds and moissanite differ significantly in their composition and optical properties, which can lead to misidentification.

Composition

Lab-Grown Diamonds: Chemically identical to natural diamonds, consisting of carbon atoms arranged in a crystal structure. They can be created through High Pressure High Temperature (HPHT) or Chemical Vapor Deposition (CVD) methods.

Moissanite: Composed of silicon carbide (SiC) and has a different crystal structure. Its optical properties differ from those of diamonds.

Testing Methods

Traditional diamond testers measure properties that can sometimes misidentify moissanite as a diamond.

Thermal Conductivity

Traditional diamond testers rely on measuring thermal conductivity, which diamonds excel at due to their atomic structure. Moissanite also conducts heat well, sometimes leading testers to incorrectly identify it as a diamond.

Optical Properties

Moissanite has a higher refractive index and greater brilliance compared to diamonds, which can confuse gemologists if they rely solely on visual inspection.

Advanced Testing

To accurately distinguish between lab-grown diamonds and moissanite, advanced gemological testing methods are required. Techniques such as spectroscopy or using specialized tools can differentiate based on chemical composition and optical properties.

The Exception: Conductivity Test

While the majority of lab-grown diamonds will not test as moissanite, there is a small exception: certain types of lab-grown diamonds can test as moissanite due to impurities during the manufacturing process.

Conductivity tests are commonly used to differentiate between mined diamonds and moissanite. However, some lab-grown diamonds, particularly those with impurities of various elements such as boron, nitrogen, hydrogen, or others, can exhibit electrical conductivity. This is more common in color- or heat-treated lab-grown diamonds where impurities are introduced.

Modern moissanite is now created using CVD technology, which is more expensive than regular HPHT or CVD stones. During the lab process, these stones may acquire these impurities, leading to conductivity.

Flawless mined diamonds are extremely rare and very unlikely to be electrically conductive. Therefore, if a diamond exhibits electrical conductivity, it is more likely to be a lab-grown diamond with impurities rather than a mined diamond.

Using conductivity tests as a definitive method can be risky, as the results are not always reliable. Gemologists should employ multiple testing methods for accurate identification.

Conclusion

Lab-grown diamonds may test as moissanite under certain conditions due to similarities in thermal conductivity. However, with the right tools and techniques, gemologists can accurately identify lab-grown diamonds. The exception of conductivity can be misleading, but understanding the underlying causes can help in distinguishing these stones.

Remember, lab-grown diamonds and moissanite are real gems created by man, and their value is determined by factors such as clarity, color, cut, and carat weight. Worrying over the minutiae of testing should be secondary to enjoying the beauty and craftsmanship of these precious stones.