Miners pose for a picture as they take a break and sit on bagged soil at a miners settlement in Anka, Zamfara, Nigeria, April 21, 2016. (Photo by Afolabi Sotunde/Reuters)





A policeman stands guard near the gold mining site in Anka, Zamfara, Nigeria April 21, 2016. (Photo by Afolabi Sotunde/Reuters)





People carry rocks to tip into a granite crushing machine in Zamfara, Nigeria, April 21, 2016. (Photo by Afolabi Sotunde/Reuters)





A granite crushing plant operates in Zamfara, Nigeria April 21, 2016. (Photo by Afolabi Sotunde/Reuters)





A man carries a headpan filled with pieces of rock at a granite crushing plant near a gold mine in Zamfara, Nigeria April 21, 2016. (Photo by Afolabi Sotunde/Reuters)





Children carry pieces of rock at a granite crushing plant near a gold mine in Zamfara, Nigeria, April 21, 2016. (Photo by Afolabi Sotunde/Reuters)





A truck is packed with crushed granite at a mining plant in Zamfara, Nigeria. April 21, 2016. (Photo by Afolabi Sotunde/Reuters)





Trucks are loaded with sand from a dry river bed behind a disused bridge in Zamfara, Nigeria April 21, 2016. (Photo by Afolabi Sotunde/Reuters)





Workers crush rocks containing gold to a fine dust at a mining site in Anka, Zamfara, Nigeria April 21, 2016. (Photo by Afolabi Sotunde/Reuters)





A herdsman climbs a tree to cut some vegetations for his animals during a shortage of grass in the mining town of Zamfara, Nigeria April 21, 2016. (Photo by Afolabi Sotunde/Reuters)





A miner crushes rocks containing gold deposits to a fine dust at a miners settlement in Anka, Zamfara, Nigeria. April 21, 2016. (Photo by Afolabi Sotunde/Reuters)





Miners process fine dust and soil as they search for gold at a miners settlement in Anka, Zamfara, Nigeria. April 21, 2016. (Photo by Afolabi Sotunde/Reuters)





Finger marks are seen in clay mud at a miners settlement in Anka, Zamfara, Nigeria, April 21, 2016. (Photo by Afolabi Sotunde/Reuters)





A man poses for a picture to show his rings of gold, silver and bronze on his fist in Zamfara, Nigeria April 21, 2016. (Photo by Afolabi Sotunde/Reuters)