Coltan is an unglamorous black rock most people have never heard of, yet it sits inside nearly every cell phone and laptop on the planet, and the Democratic Republic of Congo holds roughly 80 percent of the world's supply. Vice founder Suroosh Alvi travels into Eastern Congo to trace the mineral from the ground up, making a grueling trek to reach mining sites and meeting the armed groups who control access to them. Since the mid-1990s these militias have used coltan and other minerals to fund a conflict tied to millions of deaths, and Alvi talks with soldiers, warlords, and the laborers, including children, who dig the ore out by hand. The film keeps the camera on the physical supply chain, the pits, the porters, the checkpoints, rather than abstract politics, making the link between a rock nobody can name and the phone in the viewer's pocket explicit. It leaves the war's scale and its consumer end point sitting side by side without resolving the discomfort between them.