Smelting the Ore

By editor

Anaconda, Deer Lodge County, Montana

If you ever wondered how a chunk of rock hauled from the dark bowels of Butte’s mines ended up as a gleaming wire humming with electricity in your city, you might want to tip your hat to the Washoe Smelter in Anaconda. When it opened its doors in 1902, this smelter was the largest copper processing plant on the planet--an industrial colossus plunked down twenty-six miles west of the dusty shafts where the ore was dug. The ore arrived by rail, a grimy, heavy freight of crushed rock, and left as blister copper, a semi-refined form of the metal just shy of pure enough to be spun into wire or hammered into sheets.

The process of turning that blasted rock into something useful was no small feat. It required fire hot enough to melt the stubborn copper out of its rocky prison and air enough to keep that fire roaring. The heart of the operation was a series of reverberatory furnaces, each about the size of a small house. These furnaces burned powdered coal, reaching temperatures around 2,300 degrees Fahrenheit--hot enough to liquefy copper and separate it from the slag, the worthless byproduct made of iron oxide and silica, which looked like black glass when cooled. The molten copper was ladled out into molds to cool into ingots, while the slag was poured into huge slag pots and carted off to dumps near the smelter. Today, that slag pile looms as a black hill on the edge of Anaconda, a stubborn reminder of the enormous waste produced by the process.

The Washoe Smelter was more than just a furnace and a slag heap. It was a complex operation involving multiple steps of refining. First, the ore from Butte had to be sorted to separate the valuable copper minerals from the waste rock. High-grade ore was set aside, while lower-grade ore underwent crushing and concentration processes to separate heavier copper particles from lighter waste. These copper concentrates were then roasted in furnaces to remove part of their sulfur content before being smelted again. This smelting produced molten copper matte and slag, the matte containing the copper and iron sulfides. The matte was then sent to converter furnaces that blasted oxygen through the molten mixture, burning off the remaining sulfur and iron to yield crude blister copper--so called because of the blistered appearance of its surface caused by escaping gases during solidification.

But the smelting story doesn’t end there. Even the slag still held some copper, so it was recycled through the process to extract every last bit. The blister copper was further refined in casting furnaces and shaped into large anodes. These anodes were shipped to Great Falls, Montana, where electrolytic refining removed the final impurities--gold, silver, and other metals that had been trapped in the copper ore and smelting process. These precious metals became valuable by-products, sold to finance the entire operation.

The smelter’s towering chimney, completed in 1919 and known as the Anaconda Stack, was a marvel in its own right. At 585 feet tall, it remains the tallest masonry structure in the world, built not to impress tourists but to solve a serious problem. Before the stack’s construction, the sulfur dioxide fumes from smelting killed all vegetation for miles around. The air was thick with a choking, acrid smell that made the valley look like the aftermath of a small volcano. The stack was designed to carry these noxious gases high enough so that the wind would disperse them before they could settle on the valley floor. As Montana’s governor at the time reportedly said, “the stack will lift the poison smoke to the clouds.” It did, but that was hardly a solution to pollution--the sulfur dioxide still fell somewhere downwind, just not on the immediate vicinity of Anaconda.

The economic forces behind the smelter were as powerful as the fires inside its furnaces. Marcus Daly, one of Montana’s so-called Copper Kings, founded the Anaconda Copper Mining Company and masterminded the smelter’s construction. Daly’s vision linked the Butte mines with Anaconda’s smelting facilities and the railroads that ferried ore and copper across the country. This vertical integration was a shrewd business move--controlling mining, smelting, and transport meant controlling costs and profits. At its peak, the Anaconda Company was among the largest copper producers in the world, its operations fueling everything from telegraph wires to the electrification of America.

Yet the smelter’s fortunes were tied closely to the whims of the mining industry and national policies. In 1977, Atlantic Richfield Corporation bought the Anaconda Company, inheriting the smelter and its legacy. But times had changed. The Clean Air Act of 1970 imposed strict pollution controls, requiring smelters to install expensive scrubbers and filters to capture sulfur dioxide emissions. Atlantic Richfield saw the cost and decided it was cheaper to shut down the Washoe Smelter than to upgrade it. In 1980, the smelter ceased operations. The closure marked the end of an era for Anaconda and Butte, towns whose economies had revolved around copper for nearly a century.

The shutdown left behind a landscape scarred by industrial might--the slag pile, the towering stack, and the polluted soil. It also left a community grappling with economic decline and environmental cleanup. The stack, once a symbol of industrial progress, became a relic of the costs exacted by rapid industrialization. As historian Michael Malone wrote, “The Anaconda Company’s empire was built on copper, but it was also built on the backs of workers and the land, both of which paid a heavy price.”

To understand the Washoe Smelter is to understand the complex interplay of technology, economy, and environment in Montana’s history. It was a place where raw earth was transformed by fire and labor into wealth that powered a nation, yet left behind problems that Montana still wrestles with today.

See also

• Smelting the Ore at Anaconda, Deer Lodge County
• Contributions of the Washoe Smelter at Anaconda, Deer Lodge County
• Marcus Daly: An Irishman with Vision at Anaconda, Deer Lodge County