For anyone tracking the US–China tech war: China's lab-grown diamonds crashed the gem market — and captured the synthetic diamond that cools every advanced AI chip on Earth. Inside: how a 100-year diamond cartel collapsed, why China's 1963 industrial-diamond program suddenly matters, and the 29 days in autumn 2025 when Beijing showed the world it could shut off a supply the entire AI arms race depends on. ⏱ CHAPTERS 00:00 The Two Diamonds You Can't Tell Apart 00:31 The Crash Everyone Watched — And Why It's a Decoy 01:27 How De Beers Faked Scarcity for 100 Years 02:56 The 90% Collapse That Killed the Cartel 04:19 The Chili County Growing Half the World's Diamonds 05:46 The "Something Bigger" — The Rock That Cools AI Chips 07:08 The 29-Day Kill Switch 08:31 The Real Playbook: Rare Earths, Gallium, Graphite 09:08 What You Were Never Meant to Notice 📌 THE KEY FACTS • A 1-carat lab-grown diamond fell from ~$4,000 wholesale a decade ago to under $200 today — a 90%+ collapse. • Lab-grown went from 1% of diamond sales to a 52% majority of US engagement rings by 2024. • De Beers posted a $511M underlying loss; parent Anglo American wrote it down by $2.3B — the third straight year — and now wants out. • China produces over 90% of the world's synthetic diamond and ~95% of industrial output; more than 80% sits in Henan. • A synthetic diamond conducts heat ~5x better than copper and 13x better than silicon — while staying an electrical insulator. That makes it a heat spreader for the same class of chips the AI race is built on. • On Oct 9, 2025, China's Commerce Ministry issued Announcement 55: export controls on industrial synthetic diamond and the machines that grow it — pointedly excluding decorative jewelry. After the Xi–Trump meeting in Busan, the controls were suspended on Nov 7, 2025 for exactly one year, through Nov 10, 2026. Not withdrawn — paused, with a clock running. 🔎 PRIMARY SOURCES • China MOFCOM/GAC Announcement No. 55 (2025) and the Nov 2025 suspension notice • De Beers & Anglo American FY2025 annual results • N.W. Ayer "A Diamond Is Forever" (1947) advertising history • Industry data on lab-grown price and market share (2015–2024) • Published specs on diamond thermal conductivity and semiconductor heat-spreader use 📷 IMAGE CREDIT Xi Jinping portrait by Press Service of the President of Russia / Roman Kubanskiy, via Wikimedia Commons, licensed under CC BY 4.0. If you want the stories the headlines bury, subscribe.