A natural diamond is a crystal of pure carbon formed deep within the Earth’s mantle over billions of years under immense pressure and heat. A lab-grown diamond (LGD) is synthesized in a controlled laboratory environment over a few weeks. Both are chemically, optically, and physically identical, sharing the same crystalline structure. Distinguishing them is impossible with the naked eye and requires specialized gemological tools, as the difference in their origins leaves behind distinct, microscopic signatures.
Scientific Distinctions in Formation
The fundamental differences between natural and lab-grown diamonds stem from their creation conditions, resulting in unique trace elements and growth structures. Natural diamonds typically incorporate nitrogen, the most common impurity, classifying them mostly as Type Ia diamonds. Lab-grown diamonds, particularly those created using the Chemical Vapor Deposition (CVD) method, are often grown without nitrogen, resulting in a purer structure known as Type IIa. This difference in nitrogen content serves as a primary marker for laboratory testing.
The High-Pressure/High-Temperature (HPHT) method requires a metal solvent-catalyst, such as iron, nickel, or cobalt. Tiny remnants of this metallic flux can become trapped within the diamond crystal as it grows. These metallic inclusions are unique to the HPHT process and do not occur in natural diamonds.
The physical growth patterns also differ significantly due to the accelerated lab process versus the slow, omnidirectional growth in the earth. Natural diamonds grow in an octahedral pattern, while lab-grown diamonds often exhibit cubic or planar growth, creating distinctive internal strain patterns. These differing growth sectors become visible only when the diamond is examined under polarized light with a gemological microscope. The specific growth morphology is a primary physical indicator gemologists use to determine a diamond’s origin.
Mandatory Documentation and Inscriptions
For the general consumer, the most reliable method for identifying a diamond’s origin is through its official documentation and microscopic markings. Reputable retailers are legally required to provide clear disclosure that a diamond is lab-grown, ensuring the consumer is informed at the point of sale. This disclosure is formalized on a grading report issued by an independent laboratory.
Grading laboratories such as the Gemological Institute of America (GIA) and the International Gemological Institute (IGI) issue reports that explicitly state whether a diamond is natural or laboratory-grown. These reports detail the stone’s characteristics, including its 4Cs—carat weight, cut, color, and clarity—and confirm its method of creation (HPHT or CVD). The report acts as a verifiable certificate of the diamond’s identity.
A crucial physical marker is the laser inscription etched onto the girdle, the narrow edge of the diamond. This microscopic marking is not visible to the naked eye but can be seen with a jeweler’s loupe or microscope. For lab-grown stones, this inscription typically includes the words “LAB GROWN,” “LABORATORY GROWN,” or the abbreviation “LG,” followed by the unique grading report number. This inscription connects the physical stone directly to its certificate, offering traceability.
Specialized Gemological Testing
Professional gemologists rely on a suite of technical tests to definitively separate natural diamonds from their lab-grown counterparts. One effective method involves analyzing the stone’s reaction to ultraviolet (UV) light, specifically looking for phosphorescence. Phosphorescence is the lingering glow that persists after the UV light source is removed. Lab-grown diamonds, particularly those grown using the HPHT method, frequently exhibit a strong, long-lasting phosphorescence that can glow for several seconds or minutes. This persistent afterglow is exceedingly rare in natural diamonds, where any phosphorescence is usually faint and brief.
Magnification is another indispensable tool, allowing gemologists to examine the specific types of internal flaws, or inclusions, that reveal the diamond’s history. Under a high-powered microscope, HPHT-grown diamonds may display metallic flux inclusions, which appear as tiny, dark, opaque specks, sometimes taking on rod or amorphous shapes. These metallic remnants are a direct result of the growth environment and can cause the diamond to be slightly attracted to a magnet. CVD-grown diamonds do not have metallic inclusions but may show unique planar formations of non-diamond carbon, such as graphite. These inclusions can appear as dark, feather-like or layered structures that correspond to the diamond’s sequential growth process.
Furthermore, the microscopic laser inscription can be visually confirmed with a jeweler’s loupe, verifying the stone’s identity and matching it to its certificate. Portable screening devices are widely used in the jewelry trade as a first-line defense for identification. These instruments measure a diamond’s transparency to short-wave UV light, testing for its diamond type classification. Because the majority of natural diamonds are Type Ia, and almost all colorless lab-grown diamonds are Type IIa, the screener can quickly identify a stone that requires further, definitive testing by a gemological laboratory.