Do Lab Grown Diamonds Pass a Diamond Tester?

Lab-grown diamonds have rapidly become a popular alternative to natural diamonds, offering ethical sourcing and exceptional brilliance at a more accessible price point. As more consumers turn to these diamonds, questions arise about how they perform under traditional gem identification tools, especially diamond testers.

Can a diamond tester confirm whether a lab-grown diamond is real? Do lab diamonds behave like natural ones when tested? And how do you ensure authenticity beyond the results of a handheld device?

In this guide, we’ll explore how diamond testers work, how lab-grown diamonds respond to these tests, how they compare to moissanite, and why certification from gemological institutions like GIA or IGI remains essential for complete confidence.

How Do Diamond Testers Work？

Diamond testers are small, handheld devices used by jewelers and consumers alike to help identify gemstones. These tools typically work by measuring either thermal conductivity or electrical conductivity, depending on the type of tester.

Thermal Conductivity Testers

Thermal testers are the most commonly used type. They function by applying a heated probe to the surface of a gemstone and measuring how quickly the material dissipates heat. Because diamonds are excellent conductors of heat, a genuine diamond—whether natural or lab-grown—will disperse the heat rapidly, prompting the tester to indicate a positive result.

Electrical Conductivity Testers

More advanced diamond testers also measure electrical conductivity. These are especially useful for distinguishing diamonds from moissanite, a popular diamond simulant. While diamonds (including lab-grown ones) typically do not conduct electricity, moissanite does. This makes electrical conductivity testing a useful second layer of verification.

Some modern testers combine both thermal and electrical conductivity features, allowing users to more reliably differentiate between diamonds, moissanite, and other look-alike stones.

Do Lab-Grown Diamonds Pass a Diamond Tester?

Lab Diamond Behavior Under Testing

Yes, lab-grown diamonds do pass a diamond tester, especially thermal testers. Since they are physically, optically, and chemically identical to natural diamonds, their thermal conductivity matches that of a mined diamond. As a result, thermal diamond testers will usually identify them as authentic diamonds.

However, electrical conductivity testers may sometimes yield inconclusive or inconsistent results, especially in lab diamonds produced through the HPHT (High Pressure High Temperature) process. These diamonds can contain trace metallic inclusions from the manufacturing process, which may affect electrical readings. While such results are rare, they highlight the importance of using high-quality testers and professional gemological tools when precision matters.

Can Diamond Testers Mistake Lab-Grown Diamonds for Moissanite?

Lab-grown diamonds and moissanite may appear visually similar, but they have distinct physical and optical characteristics. With proper testing equipment, these two gemstones are easy to distinguish.

• Thermal conductivity: Both diamonds and moissanite conduct heat well, which means thermal testers alone may not differentiate between them.
• Electrical conductivity: Moissanite conducts electricity, while diamonds—natural or lab-grown—do not. This is the key factor that advanced testers use to tell them apart.
• Optical differences: Moissanite has a higher refractive index and more fire, giving it a different sparkle than a diamond.

In summary, lab diamonds are not mistaken for moissanite when using reliable testers with both thermal and electrical detection capabilities.

What Are the Limitations of Diamond Testers?

While diamond testers are incredibly useful for quick identification, they do have limitations. For instance:

• Inconclusive results can occur if the tester is not calibrated properly or if the stone has metallic inclusions (more common in HPHT lab diamonds).
• Low-end testers may struggle to distinguish moissanite from diamond due to similar thermal properties.
• Environmental conditions, such as temperature or moisture, can also affect tester accuracy.

Because of these limitations, diamond testers should not be the only tool relied upon to confirm a diamond’s authenticity, especially in high-value purchases.

Why GIA and IGI Certification Matters for Lab-Grown Diamonds?

When absolute certainty is needed, professional certification from a gemological laboratory is the most trusted method for verifying a lab-grown diamond’s authenticity and quality.

What Is a Certified Lab Diamond?

A certified lab diamond has been independently evaluated by a recognized gemological institute. These laboratories assess and report on a diamond’s 4Cs—cut, color, clarity, and carat weight—as well as its origin and any treatments it may have undergone. Certification ensures transparency, consistency, and consumer protection.

GIA Certification

The Gemological Institute of America (GIA) provides grading reports for lab-grown diamonds. These reports:

• Clearly label the diamond as “laboratory-grown.”
• Include a full 4Cs assessment
• May specify the diamond’s growth method (HPHT or CVD)

GIA-certified lab diamonds are widely trusted in the global diamond market for their objectivity and detailed grading criteria.

IGI Certification

The International Gemological Institute (IGI) is another respected institution that issues comprehensive grading reports for lab-grown diamonds. IGI certificates include:

• Complete 4Cs analysis
• Growth method disclosure
• Laser inscription details (if applicable)

IGI is commonly used by retailers for lab-grown diamonds, particularly in North America and Europe.

Conclusion

So, lab-grown diamonds can pass a diamond tester, especially when tested with thermal conductivity tools, which are designed to detect the material properties of real diamonds. While electrical testers can occasionally produce unclear results due to trace metallic inclusions, these instances are relatively uncommon.

To ensure absolute confidence in a lab-grown diamond’s identity, it's best to use both scientific tools and official documentation. Pairing a diamond tester with a GIA or IGI certificate gives you a complete picture, verifying not just that the diamond is real, but also that it meets the standards you expect.

Whether you’re a buyer, seller, or simply curious, understanding how lab diamonds are tested—and verified—can help you make more informed and confident decisions.