The country that exports a critical material usually isn't the one that mines it
In 18 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, 9 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 8 of those 9 break in 2012–2016. The trade-side origin gap also runs wide (~15–17pp), 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→74%. 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
9 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 9, 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.