The front line of America’s scramble for critical minerals lies miles beneath the surface in the cavernous tunnels of Sangdong, South Korea, where miners blast glittering seams of tungsten from craggy rock. 美国争夺关键矿产的前线位于韩国上东地下的巨大坑道内，那里的矿工们从嶙峋岩石中炸出闪闪发光的钨矿脉。…