Aug. 13 (UPI) -- Chile's El Teniente division -- the world's largest underground copper mine and operated by the state-owned National Copper Corp. -- has partially resumed operations after a collapse that killed six miners and forced a halt to production. The mine accounts for about 25% of Codelco's production, has more than 2,800 miles of underground tunnels and produced 392,000 tons of refined copper in 2024. On July 31, a magnitude-4.2 earthquake triggered a collapse that damaged 2.3 miles