The country that exports a critical material usually isn't the one that mines it
In 17 of 32 materials the top exporter is not the top miner — customs records the refiner or shipping hub, not the source, so import-origin statistics overstate how diversified supply really is. Beryllium, unwrought (🇰🇿Kazakhstan exports, 🇺🇸United States mines) · Strontium carbonate (🇩🇪Germany exports, 🇮🇷Iran mines) · Lithium carbonate (🇨🇱Chile exports, 🇦🇺Australia mines).
Concentration is intensifying — and it's testable
With the reconciled series back to 2002, 10 of 32 materials show a rising export-concentration trend that is significant on an FDR-corrected Mann–Kendall screen (23 annual points — exploratory, not confirmatory), and 9 of those 10 break in 2012–2016. The trade-side origin gap also runs wide (~15–16pp), though part of the level steps at the 2017 HS-vintage join — read it as drift, not a clean trend.
China became the processing hub, not just an exporter
China's average network throughput — its centrality as importer and broker — rose from 10% to 18% (2002–2024). Its export share of rare-earth magnets climbed 19→64%, of tungsten 9→62%. For bauxite, China's throughput rose 5→44% while its exports fell — it became the place the ore flows into. China is now the top refiner in 20 of 32 materials.
The materials with no way out
10 materials are at once hard to substitute, essentially un-recycled (<5% end-of-life) and supply-concentrated — so a disruption bites, has no secondary supply, and one country controls the flow. For 8 of the 10, that chokepoint is China's refining. They are: Rare-earth permanent magnets, Germanium, Natural graphite, Gallium, Lithium carbonate, Fluorspar, >97% CaF2, Silicon, < 99.99%, Beryllium, unwrought, Phosphorus, Coking coal.