Lab-grown diamonds (LGDs) are authentic diamonds created in a controlled laboratory setting, rather than being mined from the earth. These products are chemically, physically, and optically identical to their natural counterparts because they possess the exact same pure carbon crystal lattice structure. They share the same hardness, brilliance, and thermal conductivity as a diamond formed deep within the Earth’s mantle, with the only difference being their origin. The creation process accelerates the natural geological timeline, producing a fully formed diamond in a matter of weeks or months.
High-Pressure/High-Temperature Synthesis
The High-Pressure/High-Temperature (HPHT) method is one of the two primary techniques used to grow lab-created diamonds, directly mimicking conditions deep within the earth. This process requires a sophisticated apparatus capable of generating immense pressure and heat. Inside the growth cell, a small diamond seed crystal is placed near a carbon source, typically high-purity graphite.
The carbon source and the seed crystal are surrounded by a metal solvent-catalyst, often an alloy of iron, nickel, or cobalt. The apparatus is heated to 1,300 to 1,600 degrees Celsius and subjected to extreme pressures ranging from 5 to 6 GigaPascals (GPa). This simulates the environment approximately 150 to 200 kilometers below the Earth’s surface.
The molten metal flux dissolves the carbon source, which then migrates toward the cooler diamond seed crystal. Carbon atoms precipitate out of the solvent and deposit onto the seed, atom by atom, forming a stable diamond crystal lattice structure. This growth process typically takes several weeks, resulting in a rough diamond crystal that is then cut and polished.
Chemical Vapor Deposition Growth
Chemical Vapor Deposition (CVD) utilizes a gas-phase process rather than extreme pressure. The process begins by placing thin diamond seed plates inside a vacuum chamber, which is then filled with a carbon-containing source gas, most commonly methane mixed with hydrogen.
The environment is heated to 700 to 1,200 degrees Celsius, significantly lower than the HPHT method. Microwaves are introduced to energize the gases, creating a plasma cloud of chemically active carbon radicals. Carbon atoms within this plasma then deposit and bond onto the seed plates in successive layers.
Hydrogen gas selectively etches away any non-diamond carbon, such as graphite, ensuring the growth of a pure diamond crystal structure. Since CVD operates at lower pressures, it offers greater flexibility in the size of the growth chamber and is often favored for producing large, high-quality, colorless diamonds.
Color Modification and Enhancement
The controlled laboratory environment allows manufacturers to intentionally influence the final color of the diamond. Trace elements, known as dopants, can be introduced during the growth phase to create specific fancy colors. For instance, adding nitrogen during the HPHT process results in diamonds with yellow or orange hues.
Introducing the element boron into the growth chamber, whether during HPHT or CVD synthesis, produces a blue color. CVD-grown diamonds often contain fewer nitrogen impurities, resulting in a stone closer to colorless. However, they may sometimes exhibit a brown tint due to hydrogen-related defects.
To improve the color grade, a secondary post-growth High-Pressure/High-Temperature treatment is commonly used for stones with a yellowish or brownish cast. This process, called HPHT annealing, involves subjecting the finished diamond to high heat and pressure to alter or remove color-causing defects, transforming the stone into a commercially valuable colorless or near-colorless diamond.
Distinguishing Lab-Grown Diamonds
Because lab-grown diamonds are chemically and physically identical to natural diamonds, they cannot be reliably identified by the naked eye or with standard jeweler’s tools. Definitive identification requires specialized gemological equipment that focuses on the unique internal characteristics created by the manufacturing process.
One key identifier is the presence of metallic inclusions, sometimes trapped within HPHT diamonds from the metal solvent-catalyst used during growth. Both HPHT and CVD diamonds exhibit distinctive growth patterns that differ from the octahedral growth of natural diamonds, such as layered growth in CVD or specific cubic growth sectors in HPHT stones.
Gemologists use advanced instruments like DiamondView to observe characteristic fluorescence patterns under shortwave ultraviolet light. Infrared spectroscopy (FTIR) is another analytical tool that detects specific trace elements and subtle differences in the crystal structure that point to a lab origin. While a microscopic laser inscription often identifies a stone as lab-grown, the internal features observed through specialized testing provide definitive proof of the diamond’s creation method.