Guerrilla groups have seized control of mining areas, exploiting Indigenous people and fuelling environmental ruin on the border with Colombia Guerrilla groups have seized control of mining areas, exploiting Indigenous people and fuelling environmental ruin on the border with Colombia For months, Brig Gen Rafael Olaya Quintero, commander of the Orinoco naval force, has been chasing tin and coltan traffickers across the waterways at Colombia’s border with Venezuela . His mission has become more