Welcome news after a couple tough years as Cliffs Natural Resources today reported a 15-percent revenue increase for the second quarter. Executives say results “clearly demostrate the true power of our U.S. Iron Ore business.” Officials say Cliffs’ business advantages enabled them to achieve margins at the peak of the industry in the U-S, even as prices in Asia dropped substantially. The company runs United Taconite in Eveleth and Forbes, Hibbing Taconite and Northshore Mining in Silver Bay. This spring it reactivated an idled facility in Forbes, plus opened a new iron-pellet plant next door.