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'Natural' vs. 'Cultured' Diamonds

David Weinstein, executive director of the International Gemological Institute in New York City, examines gems with an instrument he says uses the luminescence of a diamond to help distinguish man-made from natural stones.
Nell Boyce, NPR /
David Weinstein, executive director of the International Gemological Institute in New York City, examines gems with an instrument he says uses the luminescence of a diamond to help distinguish man-made from natural stones.

Scientists are getting close to making perfect white diamonds on demand. New techniques are allowing companies to make diamonds in a laboratory -- diamonds pure enough and large enough for an engagement ring.

The precious gems have a special allure, yet they're basically just carbon atoms stuck together in a certain pattern. They're so simple that scientists have long fantasized about building them from scratch.

Scientists first tried mimicking the high temperatures and pressures that produce diamonds found deep within the Earth. That technique reliably made yellow diamonds, as well as diamond grit that's useful for things such as grinding tools. But the technique doesn't work well for white diamonds.

Apollo Diamond thinks they've found the solution to that. The company has developed a special machine for growing diamonds.

Apollo president Bryant Linares says the machine is a vacuum chamber.

“It’s a large stainless-steel can with viewports which look like viewports in a submarine. You look into and see the diamond growth.”

Linares flips a switch to demonstrate. A metal screen lifts away from the viewport, and a shockingly bright light streams out. Inside, glowing red-hot, is a cylindrical platform shaped like a soda can. On top of it, there are a few chips of diamond that look like fingernail clippings. Hovering above them is a glowing white cloud the size and shape of a softball.

“That cloud is what's called a plasma,” Linares explains. “It's similar to the type of gas that surrounds a star like the sun.”

This plasma is made by superheating a gas. The heat frees up carbon atoms that can then jump out and go somewhere more stable -- like a diamond crystal. Carbon atoms rain down from the plasma cloud onto the diamond chips. That slowly builds up the diamonds, atom by atom.

“When you see a diamond-growth process happening, it is astonishing,” Linares says. “I think the act of making diamonds is something so new and so radically different that when you do see it for the first time, it is rather stunning.”

Linares says that within days, you can get raw diamonds large enough to cut into small gemstones.

You can't leave them in longer to grow to enormous proportions because impurities will creep in over time. But that may change as the technology develops.

“What we grow is chemically, physically, and optically identical to what comes out of the Earth,” Linares says. “It is 100 percent diamond.”

It may be 100 percent diamond, but that doesn’t necessarily mean it’s 100 percent identical to what people dig out of the ground.

Putting the Gems to the Test

A dealer in New York City's famous Diamond District agreed to appraise two diamonds borrowed from Apollo, as long as he wasn't recorded.

The dealer was not informed that the diamonds were synthetic. He concluded that one was too small to be worth much, and that the other was just slightly off-color. But even after peering at them through a magnifying glass, he had no idea they were man-made.

Apollo's man-made diamonds also were assessed at the International Gemological Institute, a well-known diamond certification lab in the Diamond District.

David Weinstein says the Institute has special equipment that can distinguish a natural diamond from a synthetic one.

“We're looking for subtle differences that say, ‘There's something unusual here,’” Weinstein says.

Weinstein and his colleague Mark Yakubov perform a variety of tests on the Apollo diamonds, although they are not told where the diamonds are from

Among the testing: The diamonds are dropped into a Styrofoam cup and blasted with liquid nitrogen, then put into a machine that zaps them with pulses of ultraviolet light. Subtle differences in Apollo Diamonds' atomic structure affect how the gems interact with light.

Yakubov concludes with no doubt that these diamonds are synthetics.

“I think they are very well-made, and I think the lay person, if he saw something like this, I think it could be easily passed through as a natural diamond,” Yakubov says. “And that's the scary part.”

Synthetics Stir Up Industry Changes

Laboratories like IGI are working hard to keep up with the science of synthetics. They want to make sure they can always distinguish them from natural diamonds. But at the same time, the diamond certification labs recently made a decision that could lead to greater acceptance of synthetics.

Last month, an influential lab called the Gemological Institute of America announced that it will start issuing grading reports for man-made diamonds. It will rate them on what's called the Four C's (color, clarity, cut, and carats) just like they do for natural diamonds. IGI says it’s planning to issue similar reports.

Consumers like to see these independent reports when they're shopping for gemstones, so it might make a shopper more likely to consider a man-made diamond. But that doesn't mean the Diamond District is terribly worried about the competition.

“If your husband or boyfriend came to you with a three-carat natural diamond compared to a five-carat synthetic diamond, which would you prefer?” asks Jerry Ehrenwald, who heads the IGI lab.

Ehrenwald says that other man-made gems, like emeralds and rubies, haven't affected sales of natural stones. He thinks that synthetics just can’t capture people's imaginations in the same way.

“You can grow a synthetic diamond by order,” he points out. “You cannot go and order a natural diamond. What comes out of the earth is a gift to us from nature, a natural wonder.”

Demand for Guilt-Free Gems

Still, some people do prefer a technological wonder. Thousands of people have contacted Apollo Diamond. Bryant Linares says some potential customers just want a diamond for a little less money. Others want a stone that's not linked to bloody civil wars, or mining practices that dirty the environment.

“They believe in the future of what a cultured diamond is because it's something that is environmentally conscious, it’s socially conscious,” Linares says.

The company plans to promote its diamonds as man-made. It will laser-inscribe each gem to make sure people know it's manufactured.

But making pretty, guilt-free stones is not the main goal. Other research teams besides Apollo are working on growing large amounts of perfect diamond because they want to use its special powers for technology. Everyone knows diamonds are super-hard. But Linares says diamonds also have unique optical and electrical properties. For example, computer-chip manufacturers want to make faster chips, but that means more heat, which silicon can't handle. If the chips were made of diamond, the heat would be no problem.

“Tech applications for diamond are really the massive future for diamond,” Linares says.

For the present, it's still a challenge to make a simple gemstone. For the last three years, Apollo has been saying that it is just about ready to make its stones widely available, and their stated goal is to make half a million carats a year. But so far, they've only sold to select clients on a very limited basis.

And just try asking Linares how many diamonds they've produced so far: “That’s proprietary,” he says.

But he admits that it’s nowhere near half a million carats.

He says that production is ramping up, and that this will be the year that Apollo finally opens up sales to more of the public.

“This is very new technology,” Linares says. “We’ve produced enough that we understand the trajectory of the material. Getting to half a million carats on an annual basis is doable.”

Copyright 2022 NPR. To see more, visit https://www.npr.org.

Nell Greenfieldboyce is a NPR science correspondent.