Introduction. Cobalt is a vital resource that sits near the top of US, EU and UK lists of critical minerals1,2,3 ranked by supply-chain risk, and is a main target of government policy responses4,5,6. Cobalt has key uses in batteries, permanent magnets, superalloys and catalysts7. About 60?percent of global primary cobalt is produced in Congo-Kinshasa8, much of which is then refined in China9. Small-scale artisanal mining cruelly exploits workers and generates large amounts of toxic waste, ...