In the quiet hum of factory floors across Japan, a strategic mineral has become a measure of geopolitical gravity. China's tightening of tungsten export controls — part of a broader management of dual-use materials — has left Japanese manufacturers confronting a scarcity that no domestic workaround can quickly resolve. The metal, indispensable to everything from drill bits to semiconductor circuits, has tripled in price and fallen to a fraction of its normal supply, reminding industrial nations how deeply modern production depends on the decisions of a single dominant supplier.