Congolese miners in the jungle town of Mubi bag 50 kilogram (110 pounds) sacks of raw cassiterite, the base element of tin, in this July 24, 2004 file photo. A U.S. law on conflict minerals is curbing... more 
Congolese miners in the jungle town of Mubi bag 50 kilogram (110 pounds) sacks of raw cassiterite, the base element of tin, in this July 24, 2004 file photo. A U.S. law on conflict minerals is curbing African warlords' presence around mines in Congo, campaigners say, but its full impact remains unclear, with most firms failing to pinpoint the origin of their metals by a June deadline. Millions are estimated to have died in nearly two decades of bloodshed in eastern Democratic Republic of Congo (DRC) fuelled by the minerals smuggled through Rwanda, Uganda and Burundi. To match story MINERALS-CONFLICT/ REUTERS/Finbarr O'Reilly/Files (CONGO REPUBLIC - Tags: BUSINESS COMMODITIES POLITICS CRIME LAW CONFLICT) less 
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Reuters | Photo By FINBARR O'REILLY / REUTERS
Tue, Jul 1, 2014 2:34 AM EDT