De Beers spent a century manufacturing the scarcity that made diamonds expensive. It took China about fifty years to make that scarcity worthless — and the engagement ring was never what they were actually after. In 1888 Cecil Rhodes worked out that if you control the supply of something, you control its price. He bought South Africa's diamond mines one by one until De Beers held close to 90% of the world's rough supply, then locked millions of carats in vaults so the market never flooded. Scarcity wasn't found in the ground. It was manufactured in a boardroom. In 1947 an ad agency wrote four words that finished the job: a diamond is forever. Then someone worked out how to make more. A one-carat lab-grown stone that sold wholesale for around $4,000 a decade ago now goes for under $200 — a fall of more than 90%, and by 2024 lab-grown made up 52% of American engagement rings, against 12% in 2019. De Beers posted a $511 million underlying loss. Anglo American wrote it down by $2.3 billion for the third year running and now wants out. That is where most tellings stop, and it is the wrong story. Twenty years ago Zhecheng County in Henan grew chili peppers; it now grows a large share of the world's diamonds — and China did not build that capacity for jewellery. A diamond conducts heat about five times better than copper while insulating against electricity, which makes it the material you want under a processor that cooks itself. On 9 October 2025 Beijing placed export controls on industrial synthetic diamond and the machines that grow it, bundled with rare earths — and pointedly excluded jewellery. A month later the controls were suspended for exactly one year, expiring 10 November 2026. Not withdrawn. Suspended, with a timer.