De Beers, the 130-year-old diamond company founded by Cecil Rhodes with funding from the Rothschild family, is to start selling diamonds “grown” in a laboratory near Ascot, Berkshire.

The company, which mines billion-year-old diamonds across Africa and in the Canadian Arctic, on Tuesday launched a range of much cheaper “lab-grown diamonds” created in just three weeks by scientists using a process similar to 3D printing.

De Beers, which created the famous “a diamond is forever” slogan and once had a near-monopoly on global diamond production, said it was launching the new range of synthetic diamonds to meet demand for “affordable fashion jewellery that may not be forever but is perfect for right now”.

Facebook Twitter Pinterest The Lightbox brand diamonds will sell from $200 for one-quarter carat to $800 for a one-carat stone.

“They’re not to celebrate life’s greatest moments, but they’re for fun and fashion,” Bruce Cleaver, De Beers chief executive, said. “We have always said we are a natural diamonds business. We remain a natural diamonds business.”

The Lightbox brand diamonds will sell for between $200 (£150) for a quarter-carat stone to $800 for a one-carat stone. Nimesh Patel, De Beers’s chief financial officer, said the prices represented a 85-90% discount on the cost of natural diamonds.

“We’re not pretending they’re unique or rare,” Patel said. “If you lose it, it’s not going to hurt as much as if you lost the real thing. It is not for those great moments in life you want something inherently precious.

“If I were giving a gift to my 12-year-old daughter, I wouldn’t want to give her a natural diamond, and this a good alternative.”

The diamonds will be available for sale in the US from September. There are no plans to sell them in the UK or other markets.

De Beers has been making synthetic diamonds for industrial customers for decades but had avoided selling them as jewellery. Patel said the previous products made by De Beers’ Element Six unit were diamonds but didn’t look like them. “They are drilling tools for the oil and gas industry, and don’t look like diamonds. They are black and fit in the drill bit of tools used to drill wells.”

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The diamonds are made by a process called chemical vapour deposition. It involves pumping gases into a low-pressure vacuum. The gases react to create layers of carbon that consolidate into a single stone. De Beers said it would spend $94m creating a new Element Six factory near Portland, Oregon. When it is up and running the factory will be able to produce more than 500,000 carats of diamonds a year. Until then all the synthetic diamonds will be made in the UK.