Cobalt is used in batteries, not just for cell phones, but primarily for electric cars. The country with the largest deposits of cobalt is the Democratic Republic of the Congo.
This Wall Street Journal report shows how tech companies are making efforts to ensure mining efforts in the DRC are made safer. It should also be pointed out that the cobalt company singled out, Umicore, also supplies cobalt for the production of rechargable batteries used for electric cars. So far, no expressions of concern or efforts by environmentalists to assist in improving labor conditions in the African nation.
PHOTO CREDIT: Wikimedia