Diamonds Aren't Rare. An Ad Agency Made You Think They Were.

ONE WILD WORLD — NEWSLETTER

Issue #039   ·   Things Companies   ·   July 2026

Diamonds Aren’t Rare. An Ad Agency Made You Think They Were.

The engagement ring. The two-months’-salary rule. The word “forever” that quietly ensured you’d never sell the thing back. All of it was invented — deliberately, on paper, by a mining cartel and a Philadelphia advertising agency. And now, in 2026, the most brilliant illusion in commercial history is finally cracking.

Try selling one.

That’s the whole test. Take the diamond ring you paid several thousand for, walk it into a jeweller’s, and ask what they’ll give you. The number will be a fraction of what you paid — often a brutal fraction. Not because you were cheated at the till, and not because your stone is flawed. It’s because the price you paid was never really about the stone. It was about the story attached to it, and the story doesn’t survive the journey back out of the shop.

Which raises the obvious question. If diamonds are so rare and so valuable, why can’t you sell one?

The answer is that they aren’t rare. They never were. And nearly everything you believe about them — that you propose with one, that it should cost two months’ salary, that it lasts forever and holds its value — was invented, on purpose, within living memory, by people who were paid to invent it.

First, They Manufactured the Scarcity

Geologically, diamonds are not scarce. They are carbon under pressure, and they exist in quantities that — if released all at once — would price them somewhere closer to coloured glass. The scarcity isn’t in the ground. It’s in the release schedule.

This became an urgent problem in 1870, when enormous deposits were found near the Orange River in South Africa and diamonds were suddenly being dug out by the ton. The British financiers behind the mines realised their investment was in mortal danger: diamonds had little intrinsic value, and their price depended almost entirely on being scarce. So in 1888 they merged their interests into a single entity powerful enough to control production and perpetuate the illusion of scarcity. They called it De Beers Consolidated Mines.

The doctrine was written down. In a private memo, a young diamond buyer named Ernest Oppenheimer set out the principle plainly: the only way to increase the value of diamonds is to make them scarce — that is, to reduce the number of them that reach the market. Not discover fewer. Release fewer.

For most of the twentieth century it worked with almost comic effectiveness. De Beers bought up rough stones — its own and everyone else’s — and metered them out. It sat on a stockpile estimated in the billions, the point of which was not to sell it, but for everyone in the trade to know it existed. When Soviet geologists struck one of the richest diamond deposits ever found in Siberia in the 1950s, the USSR could have flooded the market and destroyed the cartel within a year. Instead, De Beers quietly agreed to buy nearly the entire Soviet output and channel it through London. Capitalism’s most famous monopoly and the Soviet state ran a joint scarcity operation for over thirty years.

Then They Invented the Tradition

Controlling supply keeps the price up. But you also need someone to buy the things. And here is the part that should genuinely rearrange your furniture:

The diamond engagement ring is not an ancient custom. In the 1930s, the average American engagement ring contained no diamond at all. Betrothal rings featured coloured stones, tiny chips, pearls — or nothing. Diamond sales had collapsed in the Depression.

So in 1938, De Beers hired the Philadelphia advertising agency N. W. Ayer & Son to do something unprecedented. Not to advertise a brand — De Beers sold no branded product to consumers. The brief was to sell an idea. In its own 1947 plan, the agency described the task with chilling candour: it was dealing with a problem of mass psychology, and it sought to strengthen the tradition of the engagement ring, to make it a psychological necessity.

They planted stories in newspapers about famous engagements. They lent diamonds to film stars and photographed society brides as aspirational role models. They sent a lecturer known in the trade as the Diamond Lady around America to speak to schools and women’s clubs — thousands of miles a year, radio spots, television. They even invented the pricing rule out of thin air: first one month’s salary, later two, later three. There was no ancient etiquette. An ad agency picked a number.

And then, on a late night in 1947, a copywriter called Frances Gerety sat at her desk with a deadline and no line. By her own account she put her head down and asked for help from above. She wrote four words: A Diamond Is Forever.

Colleagues complained the grammar was wrong — diamonds are forever, surely. Gerety held firm. The singular gave it the weight of a proverb rather than a sales pitch, and that was precisely the point. The line first ran in 1948. It has appeared in essentially every De Beers engagement advertisement since. In 1999 it was named the slogan of the century.

It had two jobs, and it did both at once: convince men that a diamond was the only acceptable way to propose, and convince women that a ring without one meant they were not truly loved.

It worked beyond any reasonable expectation. In 1940, roughly one in ten American first-time brides received a diamond engagement ring. By 1990, it was eight in ten. The campaign then went to Japan, where the diamond engagement ring had been essentially unknown, and manufactured the same tradition there within a generation.

And “Forever” Had a Second Meaning

Here’s the quiet genius of the line, the part that isn’t about romance at all.

A diamond that is forever is a diamond you never sell. And a diamond you never sell is a diamond that never reaches the second-hand market — never floods it, never competes with new stones, never exposes what the things are actually worth. The slogan didn’t just create demand. It quietly switched off supply from the millions of stones already sitting in drawers and on fingers.

So when you take your ring to a jeweller and recoil at the offer, you’re not discovering a scam. You’re watching the cartel premium being stripped out of the stone the moment it leaves the retail channel. And faced with that number, most people do exactly what the system needs them to do: they keep the ring. The supply curve stays clean. Forever, indeed.

The Spell Is Breaking — Right Now

For eighty years the illusion held. Then a laboratory learned to do in a fortnight what the earth takes a billion years to do.

A lab-grown diamond is not a fake diamond. It is chemically, optically and physically the same stone, graded by the same laboratories on the same four Cs, and it costs eighty to ninety per cent less. Buyers noticed. Lab-grown stones now account for a very large share of American engagement rings — by some counts approaching or exceeding half.

De Beers saw it coming and made a spectacular miscalculation. In 2018 it launched a lab-grown brand, Lightbox, priced deliberately low to signal that synthetic stones were cheap costume jewellery. The market disagreed. Lab-grown prices kept falling, the category kept growing, and in 2025 De Beers shut Lightbox down. It had built a lab-grown brand to discredit lab-grown, and lost.

The numbers now are difficult to overstate. Natural diamond prices have fallen to their lowest level this century. De Beers has been sitting on around two billion dollars of unsold stones. Its parent company, Anglo American, has written the business down by 6.8 billion dollars across three years and is trying to sell or spin it off — and is struggling to find anyone who wants it. In 2026 De Beers finally cut its official prices, having spent years keeping them well above what the market would actually pay.

The industry’s response is instructive. Producers have pledged one per cent of rough sales to a collective marketing fund, and are pushing hard on provenance, heritage, emotion — the idea that a mined stone carries a story a lab stone cannot.

Which is, of course, exactly what they did in 1938.

The scarcity was managed. The tradition was commissioned. The price rule was invented by an ad agency.

And “forever” was never about your marriage. It was about keeping your diamond off the market.

SOURCES

Edward Jay Epstein, “Have You Ever Tried to Sell a Diamond?”, The Atlantic (1982), and the book of the same name — the founding investigation of the diamond invention: artificial scarcity, the 1888 formation of De Beers Consolidated Mines, the stockpile, the Soviet agreement, and the resale problem.

Ernest Oppenheimer’s scarcity memo (quoted in Epstein): the only way to increase the value of diamonds is to make them scarce — i.e. to reduce the number reaching the market.

N. W. Ayer & Son 1947 campaign plan (quoted in Epstein and in academic study of the Ayer archive): the agency was dealing with a problem of mass psychology, seeking to strengthen the tradition of the engagement ring and make it a psychological necessity.

Academic study of the N. W. Ayer & Son archive (Miami University thesis, “Creating an Engaging Tradition”): Frances Gerety’s 1947 authorship of “A Diamond Is Forever”; Gladys Babson Hannaford, the “Diamond Lady”, lecturing across America; portraits of “engaged socialites” commissioned as role models; celebrity and film placements.

Sotheby’s — “How De Beers Changed the Diamond Market with One Simple Tagline”: before the campaign there was no unifying jewellery mandate for proposals; the slogan inherently discouraged resale and limited the secondary market; the one-month-salary rule later rising to two or three.

The Drum; Advertising Age (1999) — the slogan named #1 of the 20th century; it has appeared in every De Beers engagement ad since 1948.

Industry and historical data on adoption: roughly 10% of American first-time brides received a diamond engagement ring in 1940, versus roughly 80% by 1990; the campaign later manufactured the same custom in Japan.

Anglo American 2023–2025 annual results (as reported by Rapaport, MINING.com and Mining Weekly): $6.8bn in cumulative De Beers write-downs; 2025 underlying EBITDA loss of $511m; sale or demerger targeted for 2026.

MINING.com — “Diamond crash 2025”: De Beers left holding roughly $2bn of unsold stones; production cuts; Lightbox closed and marketing refocused on mined diamonds; the Luanda Accord (1% of rough revenues pledged to collective marketing).

TheStreet / Bank of America data — natural diamond prices at their lowest level this century; De Beers cutting official rough prices in 2026 after holding them above market.

Reporting on lab-grown diamonds (BriteCo, Edahn Golan Diamond Research, GIA/IGI grading): chemically and optically identical stones, certified on the same four Cs, at roughly 80–90% less; lab-grown now a very large share of US engagement rings.

ONE MORE THING

Like having your assumptions quietly taken apart? There’s a second newsletter from the same desk. iPrompt is a free weekly AI intelligence brief — the AI news, tools and prompts that actually matter, with the fluff cut out.

Two editions a week, five minutes each.

Subscribe free at iprompt.com →