A significant advancement in material science is the creation of real diamonds in a laboratory setting. Lab-grown diamonds are not simulants; they possess the exact same chemical composition, crystal structure, and physical properties as natural diamonds. The only difference between a natural diamond and a lab-grown diamond is its origin; one is formed over billions of years deep within the Earth’s mantle, while the other is synthesized in a controlled environment. Replicating nature’s process allows for the creation of gem-quality material for jewelry and high-performance industrial applications. This manufacturing is primarily accomplished through two distinct methods, each mimicking a different aspect of geological diamond formation.
Creating Diamonds Using High-Pressure and High-Temperature (HPHT)
The High-Pressure and High-Temperature (HPHT) method imitates the extreme conditions under which natural diamonds form deep within the Earth’s crust. This process requires a massive mechanical press capable of generating immense pressure and heat within a small internal growth cell. Necessary conditions include pressure of 5.5 to 6 GigaPascals (GPa)—equivalent to approximately 55,000 atmospheres—and temperatures ranging from 1,300 to 1,600 degrees Celsius.
The growth cell is assembled with three components: a carbon source, a metal solvent, and a small diamond seed crystal. The carbon source is usually high-purity graphite powder. A tiny diamond crystal acts as the seed, providing a template for the carbon atoms to arrange themselves into the correct tetrahedral lattice structure.
A metal alloy, typically iron, nickel, or cobalt, serves as the solvent-catalyst. When the press reaches the target temperature, this metal melts, dissolving the graphite carbon source. The system is engineered with a temperature gradient, making the carbon source area slightly hotter than the area where the seed crystal is positioned.
The dissolved carbon atoms migrate through the molten metal solvent toward the cooler diamond seed. The carbon precipitates out of the solution upon reaching the seed, crystallizing onto the surface and slowly building up the new diamond layer. This growth phase can last several days to weeks, resulting in a fully formed rough diamond.
Creating Diamonds Using Chemical Vapor Deposition (CVD)
The Chemical Vapor Deposition (CVD) method relies on a gaseous environment rather than extreme pressure to grow the diamond. This process takes place inside a vacuum chamber at low pressure, often less than one percent of atmospheric pressure, and temperatures typically ranging from 700 to 1,200 degrees Celsius.
The growth process begins with the introduction of carbon-containing gases, such as methane, into the chamber. Hydrogen gas is also introduced; it selectively etches away non-diamond carbon species, ensuring only the pure diamond structure is formed. Energy, usually microwaves, is directed into the chamber to break down the gas molecules.
This energy creates a glowing ball of superheated gas known as plasma, which contains chemically active carbon radicals. The free carbon atoms from the plasma then precipitate downward and bond to a flat diamond substrate. This deposition process allows the diamond to grow upward, atom by atom, in distinct layers.
The CVD method offers precise control over the growth environment, allowing manufacturers to manipulate the size and quality of the resulting crystal. Although the growth rate is slower than HPHT, sometimes taking several weeks, it often produces diamonds with fewer internal strain patterns. Resulting rough diamonds are often subjected to post-growth HPHT treatment to improve or alter their color characteristics.
Distinguishing Lab-Grown Diamonds from Natural Diamonds
Specialized gemological laboratories can reliably determine the origin of lab-grown diamonds. Experts rely on advanced screening equipment that detects minute differences in growth characteristics and trace elements left by the manufacturing process. These characteristics are invisible to the naked eye and require sophisticated technology for identification.
Spectroscopy and Trace Elements
One of the most effective tools is spectroscopy, including Fourier-Transform Infrared (FTIR) and photoluminescence analysis. These methods analyze how the diamond absorbs and emits light, revealing the presence or absence of trace elements like nitrogen and boron. Natural diamonds typically contain nitrogen impurities (Type Ia), while many CVD diamonds are Type IIa, characterized by a lack of detectable nitrogen.
Growth Patterns and Inclusions
Advanced ultraviolet (UV) light testing, using instruments like the DiamondView, is utilized to examine the internal growth patterns. HPHT diamonds may show remnants of metallic flux inclusions. Both HPHT and CVD diamonds exhibit unique growth sector patterns that differ from the concentric growth rings seen in most natural diamonds. These structural and elemental differences allow institutions to accurately verify the diamond’s origin, which is then disclosed on its certification report.