Lab-grown diamonds are manufactured in controlled environments but are composed of pure carbon atoms arranged in the same crystal lattice structure as earth-mined diamonds. This makes a lab-grown diamond chemically, physically, and optically identical to a natural diamond, possessing the same brilliance, hardness, and durability. Because they share these fundamental properties, distinguishing a lab-grown stone from a natural one is impossible for the average person using only the naked eye. Identification requires specific knowledge of the manufacturing process and specialized gemological tools, focusing on how the diamond was formed.
How Lab-Grown Diamonds Form
Lab-grown diamonds are created using two primary methods, each of which leaves behind different microscopic internal markers that gemologists can detect. The High-Pressure/High-Temperature (HPHT) method is designed to replicate the conditions deep within the Earth’s mantle where natural diamonds form. In this process, a small diamond seed is placed in a chamber with a carbon source and a metal solvent-catalyst, typically iron, nickel, or cobalt.
The mixture is subjected to extreme conditions, including temperatures around 1,500°C and pressures of approximately 5.5 gigapascals. The metal solvent dissolves the carbon source, allowing it to crystallize onto the diamond seed over several weeks. A sign of this method is the potential presence of tiny metallic flux inclusions trapped within the crystal structure, sometimes making the diamond slightly magnetic.
The second method, Chemical Vapor Deposition (CVD), uses lower temperatures, operating between 800 and 1,200°C. This process involves placing diamond seed plates into a vacuum chamber filled with a carbon-containing gas, such as methane, which is then heated and ionized into a plasma. Carbon atoms precipitate out of the plasma and slowly deposit onto the seed, building the diamond structure layer by layer.
The CVD process often produces diamonds that are categorized as Type IIa, a chemically pure classification that is rare in natural diamonds. The growth process leaves behind distinctive internal strain patterns, sometimes described as a “stack of pancakes,” which are unique to this method. These structural differences, which result from the rapid growth in a controlled setting, are the basis for all professional identification.
Consumer Indicators and Certification Marks
The most reliable indicator for a consumer is the official documentation that accompanies the stone, which should include mandatory disclosure of its origin. Reputable gemological laboratories like the Gemological Institute of America (GIA) and the International Gemological Institute (IGI) issue grading reports for lab-grown diamonds. These reports are just as detailed as those for natural diamonds, but they clearly state the stone’s laboratory-grown origin on the document.
A key aspect of disclosure is the laser inscription placed on the diamond’s girdle, the narrow perimeter separating the top and bottom of the stone. This inscription is microscopic, visible only under 10x magnification, and typically includes the grading report number and a clear identifier. Common identifiers include phrases like “LAB GROWN,” “LG,” or the certifying lab’s name followed by a unique number. This inscription directly links the stone to its origin report, providing a verifiable point of reference.
While a consumer cannot confirm a diamond’s origin without the paperwork, subtle visual differences can act as indicators. HPHT diamonds may exhibit dark, minute metallic inclusions that appear opaque and reflective under magnification. CVD diamonds can sometimes show faint growth striations, evidence of the layered growth process. Because these inclusions are extremely small and require an expert eye to notice, the certification report remains the most practical tool for the purchaser.
Professional Identification Tools
For absolute certainty, gemologists rely on specialized, non-destructive equipment that detects the subtle structural differences resulting from the rapid lab growth. One of the most important tools is the DiamondView, which uses short-wave ultraviolet (SWUV) light to induce fluorescence in the diamond. Natural diamonds and lab-grown diamonds react differently to this high-energy UV light, revealing distinct internal growth patterns.
HPHT-grown diamonds often exhibit a unique, long-lasting afterglow, or phosphorescence, which can appear as an orange, yellow, or greenish color after the UV light source is turned off. CVD diamonds, when viewed under deep-UV light, often display a characteristic layered or striated pattern that corresponds to the carbon deposition layers. This visual evidence of the growth structure is a definitive marker of the stone’s laboratory origin.
Advanced spectroscopic instruments provide a deeper analysis of the diamond’s atomic structure and trace elements. Techniques such as Fourier Transform Infrared (FTIR) spectroscopy and Raman spectroscopy measure how the diamond absorbs light, helping to identify minute impurities. These tools can detect the high concentration of boron that sometimes gives HPHT diamonds a bluish tint, or the absence of nitrogen typical of the pure Type IIa classification common in lab-grown stones. These instruments are necessary because a standard thermal diamond tester, which only measures heat conductivity, cannot differentiate a lab-grown diamond from a natural one.