Lab-grown diamonds have been the source of contentious debate since their conception in 1955. After the FTC’s groundbreaking verdict regarding their status, lab-grown diamonds can now boast about having the same standing as mined diamonds.
The evolution of Lab grown diamonds
Ever since their inception, the quality of lab-grown diamonds has drastically improved. The advancement of technology, along with a variety of different approaches, has resulted in two mainstream methodologies to create diamonds. The first method is known as the High Pressure, High Temperature (HPHT) growth, while the second method goes by the name of Chemical Vapor Depositions (CVD) growth. Nowadays, the CVD method is more commonly used, since it requires fewer resources or heavy-duty machinery.
Diamonds grown using the HPHT method became commercially available in the 1990’s, although their production began in 1955. The rise of HPHT-grown diamonds was attributed to lab-grown diamonds being either of low carat size or poor quality.
With the HPHT method, a carbon source, like graphite or diamond powder, is placed on top of a diamond ‘seed’. It is then put inside of a reaction chamber, accompanied by other ingredients that help facilitate growth. A catalyst allows the production process to occur at a relatively low temperature, reducing the cost of the procedure, as well as the requirement of complex machinery.
During the emergence of this procedure, a Diamond Press was built by General Electric. Its primary function was to maintain an enormous amount of pressure in a small area. In the press, a small, donut-sized chamber was surrounded by conical pistons that were capable of producing 1.5 million pounds per square inch of pressure, along with temperatures up to 2700 degrees Celsius. Metal and carbon were inserted inside the donut chamber, and a surge of electricity was run through the mixture. This electrical surge melted the carbon and metal mixture, thus starting the process of diamond crystallization.
The first diamonds that were created using this procedure were only one-tenth of a carat. Other issues in terms of the color and clarity of the lab-grown diamonds were also present. With recent advancements in growth technology, however, colorless crystals are becoming more commonplace, with carat sizes ranging up to 10 carats!
The HPHT method was slowly improved as time went on. Leaving the machines running for up to a week could produce diamonds of 1 carat. The color and clarity were also steadily improved, as it was recognized that yellow and brown colors were arising due to nitrogen. By removing all nitrogen from the system and adding aluminum or titanium powder, the crystals that formed became white. It was also discovered that including boron in the system would result in blue crystal formations.
CVD technology is a relatively new method for growing diamonds, first appearing in the market in the 1990’s. This method requires funneling a gas, such as methane, into a vacuum chamber at temperatures ranging from 900 to 1200 degrees Celsius. Graphite and carbon present in the system then react with atomic hydrogen to become activated. The activated carbon-hydrogen mix attaches itself to carbon atoms present on the diamond seed. Gradually, the carbon atoms then begin depositing, layer by layer, on the flat diamond seed crystal, whose origin was either CVD or HTHP.
Thicker crystals would take extended periods of time to grow, and sometimes interrupting the process ensured the quality of the gem. An important aspect of CVD growth is that the growth of the gem occurs vertically, not laterally. To ensure that the formed gem meets the required parameters, the seed crystal has the same diameter as the desired diameter of the gemstone. The largest known lab-grown gem using the CVD method is reportedly 9.04 carats. (Source)
The CVD method of growing diamonds showed significant structural variations as compared to mined diamonds, as well as those formed using the HPHT method. The evolution of CVD growth used a certain fact to its advantage: by changing the gas inserted in the growth chamber, the growth of more pure, colorless crystals would be the end result. Treating the crystals at higher temperatures and pressures also resulted in the removal of brown coloration in the diamonds, making them more appealing to the general public. At first, only one crystal could be grown in a CVD growth chamber, but manufacturing systems are now estimated to grow 50 or more seeds at the same time.
Lab Grown Diamonds Vs. Mined Diamonds
Lab grown diamonds have some tell-tale signs that set them apart from mined diamonds. Over time, however, CVD diamonds have become almost indiscernible from mined diamonds. The display of different graining patterns, coupled with fluorescent reactions not typically found in mined diamonds, is one of the most telling features of lab-grown diamonds. Highly advanced techniques, such as spectroscopy, are now among the few ways that distinctions can be made between lab-grown and mined diamonds. (Source)
Hardness: Diamonds are well known for their hardness; mined diamonds ranking 10 on the Mohs scale. However, lab-grown diamonds are pushing the boundaries of hardness, thus becoming less prone to damage. In 2014, some lab-grown diamonds in China were said to surpass the hardness of naturally formed diamonds. Undergoing rigorous tests, the manufactured diamonds were able to withstand about 200 gigapascals (GPa), which amounts up to twice what mined diamonds can handle!
The creation of these “nano-twinned" diamonds was set apart by their onion-like lattice structure, enabling them to withstand higher pressures, ultimately making them tougher to oxidize. (Source)
Fluorescence: Mined diamonds demonstrate a "tree-ring" like fluorescence pattern. Alternatively, they can exhibit irregular cuboid boundaries. Generally, mined diamonds show off blue, green, orange, red, or even pink fluorescence, due to the presence of impurities such as N3 or H3. Under long or shortwave UV rays, mined diamonds typically give off blue fluorescence.
HPHT diamonds exhibit luminescence due to H3, N-V, boron, or nickel defects. The fluorescence patterns occur in varying zones; the resulting 'cross-pattern' helps set HPHT diamonds apart from mined diamonds. In general terms, shortwave UV rays showcase stronger fluorescence than longwave UV rays, in which fluorescence can be absent altogether.
Contrastingly for CVD diamonds, the fluorescence differs depending on the layer of growth. The fluorescence appears in narrow luminescence bands, which are absent in mined diamonds. CVD diamonds do not exhibit any response to longwave UV rays. Given the advancement of lab-grown procedures, CVD diamonds rarely display visible fluorescence.
Structure: Mined diamonds are known for their octahedral patterns. They crystallize under temperatures of 1000-1200 degrees Celsius with pressure of 5-6 GPa, taking millions or billions of years to form completely.
HPHT diamonds showcase a mixture of octahedral and cubic growth sectors, known as cubo-octahedral growth. Such diamonds also display higher-order growth planes that are absent from mined diamonds.
CVD diamonds exhibit distinctive striations as the diamond grows as a thin film, building up layer by layer, generating terraces and steps. Parallel bands also show any interruptions that occurred in the formation pattern. (Source)