Lab-grown diamonds (LGDs) have introduced a significant challenge to the traditional methods of diamond verification in the jewelry market. These diamonds are not mere imitations, or simulants, like cubic zirconia or glass. Instead, a lab-grown diamond is composed of carbon atoms arranged in the same cubic crystal structure as a natural, mined diamond. This process, created using either high-pressure/high-temperature (HPHT) or chemical vapor deposition (CVD) methods, results in a stone that is chemically, physically, and optically identical to its earth-mined counterpart. The only difference between a lab-grown diamond and a natural diamond is their origin, which is the source of the confusion surrounding their verification.
The Verdict Do Lab Diamonds Pass Standard Testers
The straightforward answer to whether lab diamonds pass a standard diamond tester is a definitive yes. Lab-grown diamonds will register as genuine on almost all handheld thermal and electrical conductivity testers commonly used by jewelers and consumers. This is because these devices were initially designed to distinguish real diamonds from diamond simulants, which have different physical properties. Since LGDs possess the identical atomic structure of a mined diamond, they share the same physical characteristics the testers are designed to measure. The fundamental reason for this result lies in the material’s composition: both natural and lab-grown diamonds are crystallized carbon. This shared material gives them the exact same thermal conductivity profile, meaning a basic thermal tester cannot determine the stone’s origin.
How Basic Diamond Testers Function
The most common handheld devices rely on the stone’s thermal conductivity, a property where diamonds excel. Thermal testers operate by applying a small amount of heat to the stone’s surface via a heated probe. The device then measures the rate at which that heat is drawn away from the probe and dispersed throughout the stone. Diamond is an exceptional thermal conductor, dissipating heat far greater than most simulants like cubic zirconia or glass, which retain the heat. The rapid heat dissipation triggers a positive reading on the device, confirming the stone is diamond material.
Another type of handheld device is the electrical conductivity tester, which is primarily used to separate diamonds from Moissanite. While Moissanite is also a strong thermal conductor and can trick a thermal-only tester, it conducts electricity differently than most diamonds. Diamonds are typically electrical insulators, meaning they do not conduct electricity well. The electrical tester sends a current through the stone. An insulating response will confirm a diamond, while a conductive response will indicate Moissanite. Lab-grown diamonds, like their natural counterparts, are generally non-conductive and will also pass this test.
Reliable Differentiation Specialized Screening Tools
Because standard handheld devices cannot differentiate between the two types of diamonds, professional gemologists must use specialized screening tools. These advanced instruments look for minute structural and chemical markers that are a byproduct of the accelerated growth process in a laboratory. Desktop devices like the DiamondView use deep ultraviolet (UV) light to examine the internal growth patterns of the diamond crystal.
Natural diamonds grow in a generally radial, or eight-directional, manner deep within the earth, creating distinctively straight or non-uniform growth zones. Conversely, lab-grown diamonds created by the HPHT or CVD methods grow in fewer, more defined directions, often creating blocky or layered structures that are only visible under this specific UV light. Some LGDs also exhibit a phenomenon called phosphorescence, where they continue to glow for a short time after the UV light source is removed, a trait rarely seen in natural diamonds.
Spectroscopic analysis provides another method for verification by examining the stone’s chemical signature. Fourier Transform Infrared (FTIR) and UV-Visible spectroscopy can detect trace elements incorporated into the crystal lattice during growth. For instance, most natural diamonds contain trace amounts of nitrogen, whereas many lab-grown diamonds are virtually nitrogen-free. The presence or absence of specific trace elements, such as nitrogen or boron, creates a unique spectral fingerprint that reliably indicates the stone’s origin.
Advanced screening devices are also used to look for specific inclusions or defects in the crystal structure unique to the manufacturing process. For example, some HPHT lab diamonds may contain tiny metallic inclusions from the growth catalyst, a feature not found in natural diamonds. These dedicated machines look for these subtle differences in light absorption and crystal characteristics to provide an accurate, professional separation between a diamond grown in the earth and one grown in a laboratory.