Under the watchful eye of M23 rebels in the hills around the Congolese town of Rubaya, a line of men in rubber boots ferry sacks full of crushed rocks up winding paths cut into the slopes.
The labourers are hauling coltan ore, a mineral that powers the modern world. The ore will be loaded onto motorcycles and eventually shipped thousands of kilometres away to Asia. There it’s processed into tantalum, a heat-resistant metal that fetches more than $300 a kilogramme and is in high demand by makers of mobile phones, computers, aerospace components and gas turbines.
