Lab-Grown Browns Increasingly Mixed With Naturals: GSI

By Rob Bates | November 10, 2025

As De Beers amps up its campaign for the mostly brown-hued and off-color Desert Diamonds, grading lab Gemological Science International (GSI) says there’s been a spike in small lab-grown brown diamonds being mixed with natural brown stones.

“We are seeing much more brown and off-color melee, because of the marketing push. And people assume that because De Beers is advertising brown stones, [all brown melee] must be natural,” Mark Gershburg, the lab’s CEO, tells JCK. “A lot of manufacturers never thought of browns as something that could be mixed in. They don’t have the expertise that people who have been dealing with them for a long time have.”

While brown synthetics are not new, Gershburg notes that GSI has only recently been seeing a greater amount of them in smaller sizes.

“We now see it every day, in all our labs—in India, Thailand, everywhere,” he says.

Manufacturers who learn their jewelry includes lab-growns are often “shocked,” adds Gershburg.

“A lot of times, the cutters do both natural and lab-grown, and there’s no clear separation. So everything gets mixed up,” he says.

“With larger stones, it’s easy to figure out which is brown. But with smaller stones, sometimes you can have a piece with 100 stones, and you have two of them are lab-grown. With an invisible setting, you can’t just pop one out. That means destroying the piece of jewelry.

“People need to be aware what’s going on,” Gershburg says. “Manufacturers who have never dealt with these diamonds before need to be careful.”

(Photo courtesy of GSI)