Smelting the Ore

Extracting pure copper from the ores mined in Butte involved separating waste rock from valuable ore and high-grade material from low-grade material, concentrating lower-grade ore by crushing it and mechanically separating heavier metal particles from lighter waste rock, roasting copper concentrates in furnaces to remove part of the sulphur, and smelting the roasted concentrates in blast or reverberatory furnaces to remove more impurities and form molten copper matte and slag made of iron oxide and silica. The slag was poured off and cooled and granulated with water, while the molten matte was smelted in converter furnaces to create crude blister copper and more slag, which was recycled because it still contained copper. Blister copper was further refined in casting furnaces, cast into anodes, and shipped to Great Falls, where remaining impurities and metals such as gold and silver were removed, collected, and marketed. The massive black hill near the entrance to Anaconda, directly east of this site, is a slag pile. During copper smelting, the stack acted as a chimney carrying off smoke and gases produced as by-products, with exhaust from roasting, smelting, and refining furnaces passing through dust chambers and flues before going up and out through the stack. Research and development at the smelter produced more efficient methods at each stage of copper smelting, and the Washoe Smelter contributed to the growth of Montana's copper industry and helped make Anaconda known as a world leader in metallurgy.

Anaconda-Deer Lodge County, Montana · United States