Johannesburg, South Africa – As a teenager living on the East Rand of Johannesburg, Steve Chingwaru thought the flat-topped mounds of rock and earth that dotted the skyline were a natural feature of the cityscape. Jo’burg isn’t very windy, but when the wind does blow – usually around August – the air is filled with orange dust. “It gets in your hair, your clothes, your throat,” says Chingwaru.
Now, barely a decade later, the 26-year-old geometallurgist is being flown up to the city of his youth on an almost weekly basis by mining companies who want him to help them extract maximum value from the mounds of orange dust. That’s because the mounds are made up of mine waste from the richest gold deposit ever discovered, and Chingwaru has just calculated that approximately 420 tonnes of “invisible gold” – with a value of $24bn – is buried in the Witwatersrand’s mine dumps.
