De Beers tried to own lab-grown diamonds — Lightbox folded when prices fell 90%

De Beers had controlled the diamond trade for over a century when lab-grown diamonds arrived. From $4,000 per carat in 2016, synthetic stones collapsed toward $200. A disruptor was eating the market from below and De Beers had to respond. Its answer, launched in May 2018, was Lightbox — lab-grown diamond jewelry at $800 per carat. The strategy was deliberate: by calling them "fun fashion", De Beers hoped to define lab-grown diamonds as cheap accessories, not a substitute for natural stones, owning the low end while keeping the high ground for natural diamonds.

The market did not cooperate. Chinese producers scaled lab-grown diamond output to industrial levels, crushing global prices. By 2024, Lightbox had already cut its own price to $500 per carat. The following year, De Beers CEO Al Cook told Forbes that wholesale prices for lab-grown diamond jewelry had fallen 90% since Lightbox launched.

In May 2025, De Beers announced it was closing Lightbox. The Gresham, Oregon facility would be converted to industrial diamond production under subsidiary Element Six. The closure was part of a broader effort to refocus on natural diamonds as a luxury Veblen good, amid Anglo American's spin-off plan. Lightbox illustrates the limits of managing disruption from within — a company that saw the threat coming, responded, and lost anyway, because owning a market with exponential price decline is a race to the bottom.