Harmony Gold Mining Co. is willing to use debt and equity to buy a profitable mine that will offset falling production in South Africa and help fund a major new project in Papua New Guinea, CEO Peter Steenkamp said. With the company likely to lose about 40% of its current production over the next six years due to mines reaching the end of their lives, a big acquisition is “a necessity,” Steenkamp, 56, said Tuesday in an interview in Johannesburg.