The sun sets behind an oil rig seen from Monahans Sandhills State Park in Monahans, Texas, U.S., on Tuesday, June 19, 2018. In the West Texas plains, frack-sand mines suddenly seem to be popping up everywhere. Twelve months ago, none of them existed - together, these mines will ship some 22 million tons of sand this year to shale drillers in the Permian Basin, the hottest oil patch on Earth. Photographer: Callaghan O'Hare/Bloomberg