Lab-Grown Diamonds: A Century of Growth

Gemstones are among nature’s most enchanting creations, but being buried deep below mountains and hidden inside rocks, their beauty has always been hard to reach. In the ancient world, from China to India to Greece, and during the Middle Ages in both Europe and the Muslim world, ambitious experimenters sought to circumvent this difficulty by attempting to transform “base” metals into precious metals. But as those pursuits proved fruitless, duplicitous merchants would simply substitute one gemstone for another, as reported by 17th century Flemish mineralogist Anselmus Boetius, who warned gemstone buyers that white topaz could easily be mistaken for diamond. Likewise, in the Victorian era, flint glass, a variety of glass that sparkles when faceted, was used to imitate a variety of gemstones. Even today, there are numerous diamond simulants on the market, such as moissanite and cubic zirconia.

But what if we didn’t have to imitate? What if we could grow the real thing, just like nature? By the middle of the 19th century, modern chemistry had the potential to make the dreams of classical and Medieval alchemists into reality. Yet the greatest prize of all, a lab-grown diamond, would remain elusive for some time. It would take a lot of research and a little luck to get from the small and dull lab-grown diamonds of the 1890s to the large and brilliant diamonds being grown over a hundred years later, diamonds that rival nature’s greatest creations.

Early Experiments with Gemstones

Before Auguste Verneuil pioneered the Verneuil process for producing lab-grown sapphires and rubies, before Henri Moissan grew the first diamonds in his electric arc furnace, European merchants were selling lab-grown or modified gemstones produced by various methods. One early method involved simply melting down two rubies and recrystallizing them as one large ruby.

These techniques were largely informed by previous discoveries in chemistry and geology. Before the late 18th century, most naturalists believed that geological formations were the result of a great flood. But a few naturalists, such as Georges-Louis Leclerc and James Hutton, argued that geological strata—layers of rock of different age and composition—were the result of heat working deep below the Earth’s surface. These new insights, taken with early 19th century discoveries concerning the ways heat and pressure interacted with gases, led to a more accurate understanding of the formation of rocks—and eventually, the first forays into lab-grown gemstones.

Verneuil’s process was relatively simple. Chemists of the day had discovered that corundum, the mineral form of ruby and sapphire, consists of aluminum and oxygen. In the Verneuil process, aluminum oxide (Al2O3) is crushed into a powder, funneled through a tube toward a flame, and melted. The droplets of melted Al2O3 then fall onto a spinning rod, where they crystalize into a cylinder of rough gemstone. Different elements could be added to the recipe to make different colors: chromium yields a red ruby, while titanium and iron are responsible for the deep blue of a sapphire.

These lab-grown rubies and sapphires found widespread application in watchmaking, not as decoration, but as internal parts. Watches require bearings that can withstand constant use while maintaining accuracy. Corundum is an extremely durable mineral that produces little friction and needs no lubrication, making it perfect for the job. The ability to reproduce these stones in the lab made watchmaking much more cost-effective.

The First Lab-Grown Diamonds

Just as these early lab-grown stones were not always gemstone-quality, early lab-grown diamonds were too small and dull to be of any value. The method used by Moissan could not generate the necessary heat and pressure to produce anything else. Moissan used an electric arc furnace, invented in 1888 by Scottish chemist James Burgess Readman. This furnace used, as its name suggests, an arc of electricity that could heat a furnace up to 3500°C. Moissan heated charcoal in molten iron in this furnace, and then cooled the iron quickly in water. The rapid cooling of the iron produced the pressure necessary to crystallize the charcoal, forming a diamond. The process works because both charcoal and diamond are forms of carbon. The difference is that the carbon atoms in charcoal are randomly arranged in curved sheets, while the carbon atoms in diamond take on a three-dimensional crystal lattice structure. (Experiments such as this, perhaps, may also be the source of the misunderstanding that diamonds come from coal.)

Other scientists would claim to have replicated Moissan’s experiment over the next three decades, but there were few verifiable examples of lab-grown diamonds, and the diamonds that could be verified were still of poor quality. It would take one crucial technological advance in the postwar era before lab-grown diamonds could truly become a viable industry: the belt press.

Continuing Advances

After being interrupted by World War II, research into lab-grown diamonds resumed around the world, mostly in secret. In 1953, a Swedish manufacturing company grew a small diamond in a precursor to the split-sphere press, but they did not publicize their achievement. They were under the impression that no one else in the world was conducting this type of research. A year later, General Electric engineer Tracy Hall invented the belt press, a machine capable of producing 1.5 million pounds per square inch of pressure and temperatures of over 1600°C. Though that temperature is far lower than that of Moissan’s electric arc furnace, the pressure is significantly higher—enough to crystallize carbon and grow diamonds. It was precisely the replicable, verifiable advance needed to kickstart the lab-grown diamond industry. According to a Los Angeles Times article from 2008, Hall was awarded a $10 savings bond for his efforts.

These diamonds—still not gemstone-quality!—found a home in industry. Being the hardest known substance, diamond dust makes for an excellent abrasive. Saw blades used for cutting metal are often coated with a layer of diamond, and diamond scalpels are used in eye surgery and other delicate medical operations that require a high degree of precision.

By the 1970s, GE had refined their High Pressure, High Temperature (HPHT) process to the point where they could finally grow gemstone-quality diamonds. At the same time, other researchers were experimenting with Chemical Vapor Deposition (CVD), a low-temperature method of growing diamonds. Today, HPHT and CVD remain the primary methods of growing diamonds from a seed. The challenges both methods faced involved removing impurities and creating a suitably stable environment for crystal growth. No matter the method, both temperatures and pressures had to remain constant. Further research into the formation of diamond helped in this regard. In the early 1980s, different geologists published papers on the precise depth, temperature, and pressure at which diamonds grew in nature. (You can read more about HPHT and CVD here.)