Lab-grown diamonds (LGDs) are chemically, physically, and optically identical to natural diamonds, consisting of pure carbon crystallized in an isometric structure. They are not simulants like cubic zirconia or moissanite, which have different chemical compositions. The creation of LGDs in a controlled environment leaves behind microscopic signatures that allow trained professionals to conclusively determine their origin. For market transparency, the ability to detect and disclose a diamond’s origin is necessary. Detection relies on identifying subtle differences in the diamond’s internal structure and trace element composition.
Inherent Structural Differences
Detection is possible because of the differing growth environments between the Earth’s mantle and a laboratory chamber. Natural diamonds form over millions of years, typically exhibiting an octahedral growth pattern. Lab processes force growth at an accelerated rate, resulting in a combination of growth sectors. The two primary methods for creating LGDs are High-Pressure/High-Temperature (HPHT) and Chemical Vapor Deposition (CVD), and each leaves a distinct structural imprint.
HPHT synthesis attempts to replicate the Earth’s conditions by dissolving carbon in a metallic flux, which then crystallizes onto a diamond seed under immense pressure and heat. This process often results in a cuboctahedral crystal shape with multiple growth directions. These stones can sometimes contain microscopic metallic inclusions from the growth medium, such as iron, nickel, or cobalt. These metallic remnants are trapped within the crystal lattice and are never found in natural diamonds.
In contrast, CVD diamonds grow in a vacuum chamber where carbon-rich gases break down and deposit carbon atoms layer-by-layer onto a seed crystal. The CVD method primarily fosters cubic growth, often resulting in a layered, columnar structure with only one growth direction. This singular direction can cause internal strain patterns, which appear as specific cross-hatched or banded features under polarized light.
Natural diamonds often contain nitrogen atoms aggregated into small clusters. LGDs, especially those grown by CVD, tend to be Type IIa (nearly nitrogen-free), or they incorporate nitrogen and boron in ways that do not match the aggregation state found in natural stones.
Boron is often intentionally introduced to create blue Type IIb diamonds, a characteristic extremely rare in natural stones. The rapid, directional growth of LGDs incorporates impurities into the crystal lattice, creating geometric patterns. These patterns differ significantly from the random, uniform distribution found in natural stones. These subtle variations in crystal habit, strain, and impurity aggregation serve as the physical basis for all detection methods.
Advanced Detection Technology
Identifying microscopic structural and chemical differences requires specialized scientific instruments that look beyond the diamond’s surface. Deep-ultraviolet (UV) fluorescence mapping is an effective technique that reveals the internal growth structure. When exposed to short-wave UV light, LGDs often exhibit a stronger fluorescence reaction than under long-wave UV, which is the opposite of what is seen in natural diamonds.
HPHT-grown diamonds often display phosphorescence, where the diamond continues to glow briefly after the UV light source is removed. This afterglow is caused by specific lattice defects created during the HPHT process and strongly indicates laboratory origin. The precise geometric patterns of the fluorescence, such as a cross shape in HPHT or a striped pattern in CVD stones, visually map the diamond’s growth sectors.
Fourier Transform Infrared (FTIR) spectroscopy is another necessary tool, used to analyze the presence and arrangement of trace elements like nitrogen and hydrogen within the carbon structure. The FTIR instrument measures how the diamond absorbs infrared light, creating a unique spectral fingerprint. Specific peaks can confirm nitrogen in a non-aggregated state, a common signature for LGDs, or identify hydrogen-related defects characteristic of CVD growth.
Raman spectroscopy is used with photoluminescence (PL) to identify atomic defects by exciting the diamond with a laser and analyzing the re-emitted light. While the main Raman peak is the same for all diamonds, the PL spectrum reveals specific defect centers. Examples include the silicon-vacancy center in CVD diamonds or nickel-related defects in HPHT stones. These defect signatures are directly tied to the growth process and act as conclusive evidence of laboratory origin.
Screening Versus Certification
The detection of LGDs in the commercial marketplace involves two distinct levels of scrutiny: in-store screening and comprehensive laboratory certification. Screening is a preliminary, rapid test typically performed by jewelers using portable, affordable desktop devices that primarily utilize UV fluorescence. These devices are designed to quickly separate potential LGDs and simulants from natural diamonds, but they are not intended to provide a definitive, final identification.
Screening devices flag diamonds that display characteristic UV fluorescence or electrical conductivity patterns of LGDs, such as strong short-wave UV reaction or phosphorescence. If a stone is flagged as “suspect” or “refer,” it means an LGD signature was detected, and the diamond must be sent for advanced testing. If a stone “passes” the screening test, it confirms it does not display the most common LGD characteristics, but it is not a guarantee of natural origin.
Definitive identification and disclosure are provided only through comprehensive laboratory certification by independent grading organizations like the Gemological Institute of America (GIA) or the International Gemological Institute (IGI). These laboratories employ advanced spectroscopic instruments, such as FTIR, Raman-PL, and deep-UV imaging, to perform a full analysis. The certification process provides a final, legally binding determination of the diamond’s origin, which is then inscribed onto the stone’s girdle and documented in the grading report. This final step of certification is the market standard for ensuring accurate disclosure.