ханган нийлүүлэгч Рэймонд тээрэм 2019 11 5 HONG KONG Reuters Breakingviews – Rio Tinto has sounded a copper warning from the Mongolian steppe. The $104 billion mining giant says its flagship Oyu Tolgoi expansion in the country's south will be up to 30 months late, and could cost as much as a third more than planned.