Digging for leverage

A worker operating a longhole drill inside the tungsten mine in Sangdong, South Korea, on June 2. — Tina Hsu/The New York Times

THE front line of America’s scramble for critical minerals lies kilometres beneath the surface in the cavernous tunnels of Sangdong, South Korea, where miners blast glittering seams of tungsten from craggy rock.

With the highest melting point of any metal and a hardness close to that of a diamond, tungsten is essential to manufacturing semiconductors, construction and oil-drilling equipment, and the missiles and armoured vehicles used in modern warfare.