Diamond giant De Beers slashed the price of its lab-grown rocks by nearly 40%, citing their plummeting wholesale prices, the London-based company said Friday.

The man-made gems, which have gained in popularity with frugal diamond buyers, were reduced in price to $500 a carat from $800 — a 37% discount.

De Beers, which makes the lab-grown rocks under the Lightbox brand and is also the largest producer of natural diamonds, said the lower cost will be a permanent reduction.

For many years, De Beers had fought the trend towards LGDs, disparaging their quality. But in 2018 it shocked the industry when it launched Lightbox and two years later opened a $94 million manufacturing facility in Gresham, Ore.

De Beers’ bottom line has taken a hit over the past couple of years as LGD sales grew exponentially, while sales of natural diamonds declined.

In January, the company reduced the price of natural diamonds by 10% to revive sales.

The price difference between natural and lab-grown diamonds at retail is growing fast, accelerating consumer awareness that they are fundamentally very different products, Sandrine Conseiller, chief executive of De Beers brands said in a statement.

We believe that it is vital that jewelry consumers understand that lab-grown diamonds are a distinct product category, as they do not have the same enduring value as natural diamonds.

Others say De Beers’ price cut is in line with what most retailers are charging for LGDs.

De Beers is falling into line with the market, said Ria Papasifakis, head of products for New York City-based Ritani, at 25 W. 48th St.

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Ritanis LGD sales are steady and are a big part of the privately-held companys sales, Papasifakis said.

Demand for LGD pendants and earrings have only increased in recent months, the jeweler said.

Ritani charges about $500 per carat for an LGD compared with about $15,000 per carat for a natural diamond.

The two types of diamonds are impossible to tell apart with the human eye and can only be detected with special equipment.