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Image caption A conveyor belt carries chunks of raw cobalt at a plant in Lubumbashi in the Democratic Republic of Congo. Cobalt is one of those metals that define the modern world. Historically it was used to colour glass or ceramics. The Egyptians were using cobalt compounds 2,600 years ago in their sculptures. But in the 20th Century, cobalt was found to have qualities central to our most advanced technologies. Combining it with other metals produces alloys that are immensely tough, stable under extreme temperatures and anti-corrosive. So you will find it in aircraft engines, rockets, nuclear power stations, turbines, cutting tools, even artificial hip joints. That alone made it valuable... Full story

11 August