Inside the Science of Growing Diamonds

In October, a new technology lab opened amid all the digital startups in Portland, Oregon, aiming to revolutionize a centuries-old business: jewelry. “We’re continually improving our processes to create lab-grown diamonds,” says Steve Coe, a former engineer who is now the CEO of Lightbox Jewelry. “Our lab is instrumental in enabling us to conduct new kinds of research and development.”

Naturally occurring diamonds are formed by intense heat and pressure a hundred miles below the surface of the earth. But the dream of producing them on demand has been kicking around for centuries. Antoine Lavoisier, a French chemist, first discovered that diamonds consist of a crystalline form of carbon in 1772, leading to the idea that they could be grown in a laboratory. For the next 200 years, scientists attempted to do so, with little success. In the 1950s, however, scientists at Union Carbide, the Swedish company ASEA, and General Electric successfully replicated nature’s process by machine, in a matter of weeks. Since then, advances have led to various methods for creating diamonds that are chemically, physically, and visually identical to mined stones. For years, lab-grown diamonds have been used in everything from surgery scalpels to the speaker domes at Abbey Road. In 2018, Lightbox was founded to create a retail outlet for gem-quality synthetics, leading to the launch of its laboratory in Gresham, Oregon, and an optimized process to cultivating lab-grown diamond jewelry.

Sparkling Seeds

There are two methods for growing diamonds. The traditional technique is the high-pressure, high-temperature (HPHT) method. Small gem seeds are placed inside a chamber in a press, then heated to nearly 3,000 degrees Fahrenheit, at a pressure exceeding 870,000 pounds per square inch. Within the press, a carbon starting material like graphite dissolves in a molten flux of metals, lowering the temperature and pressure needed for growing diamonds. The carbon material then crystallizes on the cooler gem seed and forms diamonds. The HPHT method is tried and true, but there are downsides. By replicating how diamonds grow in nature, the method causes metal catalysts to enter the stones and create irregularities, known as inclusions, which affect color and sparkle. Additionally, the process is costly due to the energy and equipment involved.

By contrast, Lightbox’s lab-grown diamonds use the chemical vapor deposition (CVD) method, which produces colorless crystals. CVD was initially viewed with skepticism in the industry. In nature, carbon needs high pressures and temperatures to turn into diamonds. While the CVD method involves high temperatures, the process takes place in a near vacuum at low pressure—an environment that would never produce a diamond geologically. But after decades of research into balancing the chemical reactions in the process, the Lightbox team figured out how to grow a large gemstone in just weeks.

With CVD, Lightbox scientists calibrate pressure and temperature while monitoring the process through windows in the heating chamber. The lab team places tiny slivers of lab-grown diamonds into a custom CVD reactor. They then use microwaves to create ionized gas, developing a stable source of heat to do in days what typically takes centuries. “Think of it as a controlled ball of lightning,” Coe says.

When the temperature in the wardrobe-size reactor reaches 6,000 degrees—two-thirds as hot as the surface of the sun—the gas molecules break apart, and carbon molecules rain down and bond to the seeds, growing them one layer at a time. Powered by hydroelectric energy, the vacuum chamber blends extreme heat, low pressure, and a unique mix of gases to grow rough diamonds large enough to yield one-carat polished stones used in pieces like a Solitaire Gold Pendant in about two weeks. “It’s not an easy thing to do,” says Coe, who helped pioneer CVD in the 1990s. “But our proprietary technology enables us to keep the reactor stable for long periods of time to create beautiful diamonds.”

Software to Shine

Once a diamond has been produced, Lightbox scientists use software to digitally scan and assess each one. To the untrained eye, an unpolished diamond resembles a dull piece of glass. So scientists use lasers to transform each one into a sparkling stone in a four-part process.

First, Lightbox technicians analyze the stones to determine the best way to cut them. Then lasers are used to remove the desirable central portion, “coring” the diamond for further molding. The core is either sliced into slivers to produce more diamonds or shaped into a finished gem. Finally, a technician adds the remaining facets and a polisher smooths all the surfaces.

With each lab-grown diamond, Lightbox engineers refine the process. They collect data with each stone and use it to improve the techniques that go into pieces like the one-carat solitaire studs. “We’re always trying out new approaches,” Coe says. “Continuous improvement is everything to us.”

The Perfect Color

Lightbox scientists use chemistry to imbue their diamonds with a range of beautiful colors—a rarity in nature. For centuries, diamonds got their colors from defects and impurities. Pure diamonds—like pure carbon—are colorless when formed underground. But when elements like nitrogen get trapped in the crystalline structure as it’s forming underground, the process can create a yellow or brown stone. When the surrounding earth’s radioactivity embeds electrons during the process, green diamonds can be created. And a process known as plastic deformation—carbon atoms displaced in extreme temperatures, changing the way electrons absorb light—is thought to yield pink diamonds. Yet no reaction in natural diamonds is rarer than when boron enters the process and creates a blue gem—an irregularity found in just one out of every 200,000 diamonds in the world.

Colored diamonds have long been studied by scientists, resulting in a deep body of research, which Lightbox draws upon to concoct its own hues. Using proprietary blends of gases and post-growth treatments, the team treats each diamond with a different mix to create colors like soft blue and blush pink. “We can modify diamonds at the atomic and molecular level to enhance their color,” Coe says. “Some colors are more difficult to create than others, but we’ve developed a process for our blue and pink diamonds that enables us to achieve them at scale.”

Ultimately, Lightbox uses science to accomplish an incredible feat: offering world-class lab-grown diamonds for any price point. Inspected 70 times and inscribed with a mark of quality undetectable except with a 10x magnifying loupe, the diamonds are sold for $800 a carat and set into a variety of beautiful Lightbox jewelry pieces. And Lightbox is working on more innovations, ensuring new types of lab-grown diamonds continue to be grown in the future. “We’re focusing on more colors and growing larger stones,” Coe says. “Our new lab is instrumental. Across the board, we’re seeing customers embrace our diamonds in their fashion and everyday jewelry.”

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This story was produced by WIRED Brand Lab for Lightbox Jewelry.