In the dark, hot, cramped tunnels nearly 4 km underground, workers excavate a thin dipping vein of gold ore. Rock is taken to the surface and the gold is extracted using a process that can be traced back to the 1880s: the ore is crushed and sprayed with cyanide to leach out the gold metal.
Demand has never been higher, but nearly all the easy gold has already been mined. So, to maintain production, mining companies are turning to more difficult sources that would have been left in the ground if gold prices had been lower. From the depths of TauTona in the South African veldt, all the way up to Pierina in the Peruvian Andes, 4,100 metres above sea level, miners are digging deeper than ever before, going to more remote locations and politically volatile regions.

At the same time, significant amounts of gold can easily be obtained without digging into the earth at all — just by recycling the gold buried in the growing mountains of discarded electronics. The advent of more efficient ways to recycle gold from gadgets has turned scrap into a major source of the precious metal.