Diamonds, geologically, are not rare. They are common carbon under pressure, present in volumes that would price them somewhere closer to coloured glass if released at once. The scarcity that sustains the modern market is not in the ground. It is in the release schedule, and it was written down, in plain language, in a private memo by a young diamond buyer named Ernest Oppenheimer in the early 20th century.
Oppenheimer, posted to Kimberley, South Africa, articulated a principle that would shape the industry for generations. According to historical accounts, he believed controlling diamond supply was essential to maintaining their market value, and he structured De Beers’ operations around limiting production to preserve scarcity. He was not describing a market. He was describing a method.
Oppenheimer would eventually control De Beers, the company founded by Cecil Rhodes that already dominated South African mines. By the 1930s, his cartel, the Central Selling Organisation, later the Diamond Trading Company, was buying up stones from producers around the world, locking them in London vaults, and metering them out at a pace the cartel chose. The memo was the doctrine. The vaults were the proof.
The sentence that built a century
Oppenheimer’s logic was almost embarrassingly simple. Diamonds, geologically, are not rare. They are carbon under pressure, and by the late 19th century, South African finds had flooded the European market so completely that prices were collapsing. Rhodes had already consolidated the mines to stop producers from undercutting one another. Oppenheimer’s contribution was to formalise the next step: if supply could be choked at the source, demand would do the rest.
The memo, quoted in Edward Jay Epstein’s 1982 investigation for The Atlantic, “Have You Ever Tried to Sell a Diamond?”, became the operating manual for an industry that has since sold the idea of rarity to roughly every couple in the Western world. Geologists have understood for decades that gem-quality diamonds exist in volumes that, if released at once, would price them somewhere closer to coloured glass.
How the vault actually worked
For most of the 20th century, the mechanics ran like this. De Beers bought rough stones from its own mines and from independent producers. When new deposits appeared, De Beers either signed exclusive marketing deals or, where it could, bought up the surrounding production to keep the new supply inside the system. The stones travelled to London. At sorting houses, they were graded and divided into parcels. Several times a year, invited buyers, “sightholders”, arrived to receive boxes whose contents and prices De Beers had set. The buyer could accept the box or refuse it, and refusal meant not being invited again.
Stones the cartel did not want on the market simply stayed in the vault. At various points in the 20th century, the stockpile was estimated in the billions of dollars. The point of the stockpile was not to sell it. The point was that it existed, and that everyone in the trade knew it existed.
The Soviet problem
The doctrine’s hardest test came in the late 1950s, when geologists in Yakutia struck a kimberlite pipe that turned out to be one of the richest diamond deposits ever found. The Soviet Union, hostile to Western capital and indifferent to De Beers’ price discipline, could have flooded the market and broken the cartel within a year.
Instead, De Beers signed a quiet agreement to buy almost the entire Soviet output, channel it through London, and meter it into the market alongside its own stones. The arrangement held, through middlemen and shell companies, through the Cold War. Capitalism’s most famous monopoly and the Soviet state ran a joint scarcity operation for more than thirty years.
Why scarcity makes a stone feel valuable
Oppenheimer’s instinct ran ahead of the academic literature by half a century. The behavioural research that now describes what he was doing came later, and it confirms the shape of the trick. Limited availability raises perceived value and urgency in ways that are largely independent of the object itself, a pattern documented across consumer behaviour studies on scarcity effects.
The same principle shows up in relationships, where psychologists describe a scarcity principle that makes harder-to-reach people feel more desirable. Forbes summarised the same research for a general audience in a 2024 piece on love’s scarcity principle. The mechanism is the same one Oppenheimer used on a stone. Restrict the supply, and the brain interprets the restriction as evidence of worth.
Once a buyer has paid the scarcity premium, a second bias steps in to defend the purchase. The sunk cost fallacy, the human tendency to keep valuing something in proportion to what was spent on it, keeps the diamond on the finger and out of the resale market, which is exactly where the cartel needed it to stay. A stone that gets resold is a stone that competes with new supply.
The advertising half of the doctrine
Choking supply only works if demand is steady. In 1947, the N.W. Ayer advertising agency, working for De Beers, produced the four words that locked the demand side in place: “A Diamond Is Forever.” The copywriter was Frances Gerety. She had been asked to come up with a line that would discourage women from ever selling their diamonds and discourage men from buying second-hand.
The campaign worked on two fronts at once. It told couples that a diamond was the only acceptable engagement stone, a tradition that had grown dramatically through the 20th century. And it told them that selling the stone later would be a kind of emotional betrayal. The second message protected the first. If nobody resold, the only diamonds on the market were the ones De Beers chose to release.
What a diamond is actually worth
Anyone who has tried to sell a diamond back to a jeweller learns the doctrine in a single afternoon. The resale price is typically a fraction of the retail price. The gap is not fraud. It is the cartel premium being stripped out of the stone the moment it leaves the retail channel.
This is where the sunk cost trap does its quiet second job. Faced with a resale offer that reveals the original markup, most owners simply keep the stone. The diamond stays in a drawer or on a finger for another generation, and the supply curve stays clean.
Even theologians have started using the framing. A recent reflection in America magazine borrowed the term to describe spiritual stubbornness, citing the sunk cost fallacy as a lens on bad decisions people refuse to abandon. Oppenheimer would have recognised the dynamic. He built a business on it.
The cartel’s slow unwinding
The Oppenheimer doctrine held, in its purest form, until roughly the early 2000s. Several things broke it at once. Australia’s Argyle mine walked away from the De Beers selling arrangement in the 1990s. Canadian mines in the Northwest Territories opened in the late 1990s and sold directly. Russia’s Alrosa, after the Soviet collapse, eventually negotiated its own terms. The European Commission forced De Beers to stop buying Alrosa’s rough.
De Beers’ market share, which had been dominant for most of the 20th century, fell significantly by the 2010s. The Oppenheimer family sold its remaining stake in the company to Anglo American in 2012, ending more than 80 years of family control.
And then lab-grown diamonds arrived at scale. By the mid-2020s, a chemically identical stone could be produced in a reactor in a few weeks at a fraction of the mined price. The scarcity Oppenheimer had constructed around mined stones could not be constructed around stones that anyone with a CVD chamber could grow.
The doctrine outlives the cartel
The interesting thing about the memo is that the underlying idea, that perceived value can be manufactured by controlling release, did not die with the cartel. It moved. Luxury watchmakers run waiting lists for steel sports models that cost less to make than the brand’s gold dress watches. Sneaker companies destroy unsold stock rather than discount it. Limited editions, drop culture, allocation lists for handbags, NFT mint caps. All of it is Oppenheimer’s sentence applied to a different material.
Somewhere in a London archive, the original memo sits as a single page of typescript, the plainest possible language working out a problem on paper. In a vault not far from it, stones the cartel chose not to sell still rest in their parcels, graded and counted, waiting on a release schedule that no longer holds. The doors are quieter now. The diamonds are still there, in the dark.
