Is coltan - the notorious conflict mineral from which these two metals are derived - still being smuggled from DR Congo into Rwanda, to evade taxes and sourcing controls? Laurence Knight investigates the hi-tech roles to which these two chemical elements are put in gadgets and telecommunications. He also discusses the bloody history behind the mining of their ore in the heart of Africa with Sophia Pickles of human rights organisation Global Witness. And the BBC challenges the Rwandan authorities and chipmaker Intel about what they are doing to address allegations of current-day smuggling of coltan across the border from Congo to be laundered in Rwanda.

(Picture: A miner cleans freshly dug coltan ore at the Abahizi cooperative mine in Ngara, Rwanda)