Lab-grown diamonds (LGDs) are pure carbon crystals with the exact same chemical composition and atomic lattice structure as their mined counterparts. They are synthesized in controlled environments using processes that mimic the intense heat and pressure deep within the Earth. This structural identity between natural and lab-grown stones has created considerable confusion for consumers and jewelers attempting to verify their purchases and origins. This article examines whether these modern stones can be successfully identified using common, handheld devices.
The Nature of Lab-Grown Diamonds
The synthesis of LGDs primarily uses two methods: High-Pressure/High-Temperature (HPHT) and Chemical Vapor Deposition (CVD). HPHT simulates geological conditions, dissolving carbon in a metal flux solvent and allowing it to crystallize onto a seed diamond. The CVD process involves breaking down hydrocarbon gases in a vacuum chamber, allowing carbon atoms to deposit layer by layer onto a substrate.
In both methods, the resulting product is a crystalline structure composed of carbon atoms arranged in a stable, three-dimensional cubic lattice. This perfect arrangement of atoms means that LGDs possess physical properties indistinguishable from natural diamonds at a fundamental level. This identical atomic structure makes diamond the best known natural conductor of heat among all bulk solids.
This property, known as thermal conductivity, is the mechanism that allows heat to rapidly move through the crystal structure. The ability of the diamond lattice to efficiently dissipate heat is the primary reason why distinguishing between natural and synthetic stones poses a challenge for basic testing equipment. Diamond’s thermal conductivity is significantly higher than that of most diamond simulants.
How Standard Diamond Testers Function
Standard handheld diamond testers used by jewelers and consumers operate predominantly on the principle of thermal conductivity. These devices use a heated thermistor tip placed against the stone’s surface to measure the rate at which the stone draws heat away. If the stone rapidly dissipates the heat, it is registered as a diamond due to superior thermal conductivity.
These devices were designed to differentiate diamonds from poor heat conductors like cubic zirconia or glass. Since these simulants have significantly lower thermal conductivity, they retain heat longer at the probe’s tip.
A second, less common type of standard tester measures electrical conductivity. This test is primarily used to differentiate diamonds from Moissanite, a popular simulant that also has high thermal conductivity. Moissanite is an electrical conductor, while most diamonds are electrical insulators. However, the vast majority of inexpensive handheld testers rely solely on thermal dissipation measurement.
The Result: LGDs and Standard Testers
A lab-grown diamond unambiguously passes a standard handheld tester. Because LGDs possess the same superior thermal conductivity as natural diamonds, they dissipate heat from the probe at an identical, rapid rate. When the thermistor tip touches an LGD, the instrument registers the rapid heat loss and illuminates the “diamond” indicator.
The instrument measures a physical property that is identical for both natural and synthetic stones. This highlights the limitation of basic instruments in the modern marketplace. Testers can reliably distinguish a diamond from a non-diamond simulant like cubic zirconia, but they cannot distinguish between the two types of actual diamonds.
The confusion arises because these testers were not engineered to detect differences in the crystal’s formation history. The identical thermal response means that for a simple handheld test, the lab-grown stone is functionally the same as a mined stone. Advanced methods are necessary to verify origin, as basic thermal properties are shared.
Differentiating LGDs: Specialized Screening Tools
Since basic thermal testing is insufficient, specialized screening tools are required to definitively identify a lab-grown diamond. These advanced instruments do not measure thermal conductivity; instead, they look for microscopic evidence of the stone’s synthetic origin. One common method utilizes ultraviolet (UV) fluorescence analysis, which reveals the internal growth structure of the diamond.
Natural diamonds typically show uniform fluorescence patterns, while LGDs often exhibit distinct cross-hatching, banding, or hour-glass patterns corresponding to the different growth sectors formed during the HPHT or CVD process. Specialized screening devices also use shortwave UV light to detect trace elements and defects.
These impurities cause unique light reactions, such as phosphorescence, which is a subtle glow that persists after the UV light source is removed. Natural diamonds frequently contain nitrogen impurities, while many CVD-grown diamonds contain small amounts of silicon, and HPHT diamonds may contain metallic inclusions from the growth environment.
For definitive laboratory confirmation, techniques like Fourier Transform Infrared (FTIR) Spectroscopy or Raman spectroscopy are used to analyze the molecular vibrations and impurities within the diamond lattice. These methods examine the subtle structural and chemical differences that are a result of the stone’s formation history, reinforcing why simple testers are no longer adequate for origin determination.