Start with the number, because the number is the story. In 2001, when it was taken private, De Beers was valued at more than $18 billion. In 2011, Anglo American bought out the Oppenheimer family on terms that valued the company at nearly $13 billion. In late July 2026, Anglo was reported to be negotiating the sale of its 85 per cent stake for roughly $1 billion, with only about $750 million paid up front.

The mines did not run dry. The stones did not stop sparkling. Something else lost its value, and that something was a brand.

The branding of diamonds is the eighty-year effort, led by De Beers and its advertising agencies, to make a mined carbon crystal stand for eternal love, and to make an engagement without one feel incomplete. What follows is how that brand was built, who built it, and what is now dismantling it.

Exhibit A: a meeting in New York, 1938

Diamonds had symbolised betrothal long before advertising existed. The first well-documented diamond engagement ring belongs to Archduke Maximilian of Austria, who gave one to Mary of Burgundy in 1477. But for most of history it was an aristocratic habit, not a mass expectation. Before the Second World War, only around one in ten American engagement rings contained a diamond.

The turning point came in 1938. Harry Oppenheimer, of the family that controlled De Beers, met the president of the advertising agency N. W. Ayer & Son in New York. The advertising began in 1939.

Read the brief carefully, because it is unusual. De Beers did not ask Ayer to promote De Beers. It asked Ayer to promote the diamond itself.

At that point the company controlled somewhere between 80 and 85 per cent of the world’s rough diamond distribution. Whoever sold a diamond, De Beers had probably sold it first. So the smartest brand strategy was to make the category famous and let its own name stay out of the light.

Ayer’s tools were product placement, Hollywood stars wearing diamonds, and associations with royalty. American diamond sales rose from $23 million in 1939 to $2.1 billion by 1979.

Exhibit B: four words written in 1947

In 1947 an Ayer copywriter named Frances Gerety wrote the line that did the heaviest lifting: “A Diamond Is Forever.”

It is a remarkable piece of engineering, and it works on two levels. On the surface it is romance: your love, like this stone, will last. Underneath it is supply control.

If a diamond is forever, you do not sell it. You keep it, pass it to your children, and never release it back into the market where it could compete with new stones. Every grandmother’s ring locked in a drawer was one less diamond pushing prices down.

Critics have long pointed out that diamonds can be chipped, shattered, discoloured or burned. The slogan never claimed otherwise. It made a promise about feelings and let the customer supply the physics.

In 2000 the advertising trade press named it the best slogan of the twentieth century. It probably inspired a James Bond title too.

"Forever Present", a De Beers Group holiday film that still works the word "forever" more than seventy years after Gerety wrote the line.

Exhibit C: the price tag on love

A myth needs a rule, so the campaign supplied one. In the 1930s De Beers suggested a man spend roughly one month’s income on an engagement ring. By the 1980s the guidance in America had risen to two months. In Japan it was three.

Notice what a salary benchmark does. It turns an emotional decision into an apparent obligation, and it scales automatically with the buyer’s wealth. Picture a young engineer in Jurong in 1985, totting up his pay slip at a jeweller’s counter. He is not choosing a stone; he is passing a test someone else designed.

Then came the add-ons: the eternity ring, the trilogy ring, the right-hand ring. Each was a new occasion invented to sell more stones. Eternity rings, set with up to 25 small diamonds, were aimed at older married women and conveniently absorbed the flood of small stones arriving from Soviet mines.

Exhibit D: Japan, where the tradition was built from scratch

If you want proof that the diamond ring is a brand rather than a timeless custom, look east.

Japan did not legally allow diamond imports until 1959, and there was no tradition of engagement diamonds at all.

When De Beers and its agency J. Walter Thompson began campaigning in 1967, about 5 per cent of Japanese brides received a diamond ring. By 1972 the figure was 27 per cent. Within fourteen years it was 60 per cent.

The creative strategy was explicit. Magazine advertisements showed Western-looking women in European clothes, doing things that broke with Japanese tradition. The diamond was sold as a ticket out of the past and into modern life.

One of the oldest wedding cultures on earth acquired a new “tradition” inside a generation.

Chinese-speaking markets were next. Chow Tai Fook, founded in Guangzhou in 1929, obtained a licence to buy diamonds from De Beers in 1964, and by the 1970s it was buying around 30 per cent of Hong Kong’s diamond imports.

So is a diamond ring actually a scam?

Ordinary people ask this whenever diamonds come up, usually followed by somebody’s story about trying to resell a ring and being offered a fraction of its price.

The arguments are familiar. Expensive rings are pure signalling. Gem prices have always been propped up while industrial diamonds stay cheap. And if lab stones are flawless, what exactly is the premium for?

The fairer verdict: a diamond is real, hard, rare in nature and beautiful. What was manufactured was the meaning: the rule that love requires one, the benchmark for its cost, and the idea that it must never be sold. That meaning was the product, and it was worth billions.

The economics of marriage do not flatter the myth either. Among thousands of ever-married Americans, higher spending on the engagement ring and the wedding goes with shorter marriages, not longer ones. Association, not cause. Still, “forever” seems to sit more comfortably with a modest receipt.

The first crack: competition, then conscience

The monopoly eroded slowly. By 2000 De Beers’ share of world supply had fallen to 63 per cent. By 2019 its share of the rough market was 29.5 per cent, down from as high as 90 per cent in the 1980s. After the 2008 financial crisis, Russia’s Alrosa even overtook it by carats mined.

Then came the reputational blow. Diamonds mined in war zones and sold to fund violence put a dark shadow on the romantic story. In 1999 De Beers stopped buying diamonds on the open market to guarantee its own stones were conflict-free, and the international Kimberley Process certification scheme took effect in 2003. The company rebuilt part of its pitch around provenance, launching the Forevermark brand in 2008, with each stone carrying an invisible inscription of an icon and serial number, one twentieth of a micron deep.

That was a real shift. For seventy years De Beers had sold the generic diamond. Now it needed its own name on the stone, because the category story alone was no longer safe.

The second crack: diamonds from a reactor

The real threat had been sitting in a laboratory since General Electric produced gem-quality synthetic crystals in 1970. For decades they were expensive and small. Then production costs collapsed, much of it in China, where officials claim Henan province accounts for around 80 per cent of national output, and in India.

In July 2018 the US Federal Trade Commission removed the word “natural” from its definition of a diamond. A lab-grown stone was, legally and chemically, a diamond. The gemmological establishment followed, dropping “synthetic” from its lab-grown reports in 2019.

De Beers’ reply was the most interesting brand experiment in its history.

In May 2018 it launched Lightbox, selling lab-grown stones in pink, blue and white at $200 for a quarter carat and $800 for a carat, roughly a tenth of the price of its natural stones. Its chief executive described the line as fashion jewellery that may not be forever but is perfect for right now.

That phrase was a deliberate act of brand defence. By pricing synthetics as cheap, cheerful trinkets, De Beers tried to draw a fence: lab-grown for parties, natural for proposals. It was the old “forever” strategy turned inside out.

It did not hold. Pandora, the Danish jewellery giant, announced in 2021 that it would stop using mined diamonds and switch to lab-created stones. By 2023, lab-grown diamonds made up around 17 to 18 per cent of the global diamond jewellery market, up from about 2 per cent in 2017.

By 2024, analysts estimated that roughly half of American engagement ring stones were lab-grown. Lab-grown prices fell 74 per cent between 2020 and early 2025, leaving the gap with natural stones at around 90 per cent. In May 2025 De Beers closed Lightbox.

Its own cheap diamond was now too expensive to compete.

What happens to a brand when the scarcity disappears?

Every luxury brand rests on something hard to copy. For diamonds, it was rarity plus a story. Lab-grown stones removed the rarity in the eye of the buyer, because a newly engaged couple cannot tell the difference without a machine. That left the story to carry the full weight, and the story had been written for a world without a cheaper identical twin.

The fallout reached the balance sheet fast. Anglo American announced its intention to sell the business in May 2024, wrote down De Beers by $2.9 billion that year and took a further $2.3 billion impairment in 2025. By 2025 De Beers was sitting on around $2 billion of unsold mined diamonds.

Botswana, which already owns 15 per cent and produces more than 70 per cent of the company’s diamonds, has a right of first refusal on the stake.

In July 2026, a consortium led by former De Beers chief executive Gareth Penny was reported to be Anglo’s preferred bidder, promising a strategy centred on natural-diamond mining and marketing. As of October 2026, no deal had been confirmed.

The new story: origin, colour and Africa

De Beers’ current playbook tells you what the industry thinks still works. In June 2025 it formally launched “Origin, De Beers Group”, a programme that lets buyers see their diamond’s country of origin and its path through the supply chain, backed by blockchain tracking, along with the social programmes their purchase supported. In the same month it unveiled Ombré Desert Diamonds, its first new jewellery concept in more than a decade, featuring stones in champagne, honey and whiskey tones from the Kalahari and Namib deserts.

Industry sceptics suspected the brown-stone push was partly about clearing lower-colour inventory, which De Beers denied. But the logic is clear enough.

Lab-grown production has concentrated on colourless stones. Natural brown and golden diamonds look different, and they come with a place, a people and a story. Provenance and imperfection are hard to synthesise.

That is the real lesson for brand owners. When your product can be copied exactly, your brand has to sell what cannot be copied: origin, time, human consequence. “Forever” was a claim about the stone. The next diamond brand will have to be a claim about where it came from.

Questions from the evidence room

Who created the slogan “A Diamond Is Forever”?
Frances Gerety, a copywriter at the agency N. W. Ayer & Son, wrote it for De Beers in 1947. It was later named the best advertising slogan of the twentieth century.

Are lab-grown diamonds real diamonds?
Yes. They are chemically and physically diamond, and in 2018 the US Federal Trade Commission removed “natural” from its definition of a diamond. They are typically far cheaper than mined stones.

When did diamond engagement rings become common in Asia?
In Japan, De Beers campaigns from 1967 lifted diamond rings from about 5 per cent of brides to 60 per cent within fourteen years. In Hong Kong, the jeweller Chow Tai Fook began buying directly from De Beers in 1964.

Every brand eventually meets its lab-grown moment. Firefish’s brand audits find the claims yours can still defend.