The Tanzanian gemstone mined by child labour
19 June 2014 Last updated at 22:16 BST
The precious blue tanzanite stone has become one of the most coveted gemstones in the world, and is only found in Mererani in northern Tanzania.
Its mining industry generates over $1bn a year, but the working conditions are tough, especially for the underage miners who are being employed illegally.
The BBC's Aboubakar Famau reports from Mererani.