Willoughby: Smelters wring a stream of silver from solid ore
May 12, 2018
You can't make a silken purse out of a sow's ear, but it seems like it would be simple to transform solid ore into streams of pure silver. You just melt it, right? Many assay shops in Aspen maintained small furnaces to melt ore samples, but on a larger scale, complications arose.
Aspen's smelting industry never caught up to the stellar achievements of its ore production. During the 1880s, an attempt to finance, build and operate a smelter failed to compete with the cost of transporting ore by mule train over mountains to Leadville for smelting. Aspen's first, small smelter operation could not match Leadville's expertise. They had begun to successfully smelt minerals during the late 1870s. By the mid 1880s, when Aspen's ore production escalated, local mines leveraged Leadville's equipment and experience. When the railroad arrived and the cost of shipping dropped, the Leadville option made even more sense.
During the early 1890s, two new smelters opened in Aspen. One, the Hardinge Smelter, bought and remade the original one. H.W. Hardinge had operated a smelter in Leadville and had improved methods for dealing with slag, an unwelcome byproduct. Aspen's ore contained large amounts of silica that became slag when melted. After the molten slag had drained from molten lead and silver, it still contained silver, 5 to 6 ounces of the valuable metal per ton of slag. Hardinge's process retrieved that last bit of silver and profit. When he first opened the old smelter, Hardinge took several months to melt the slag and retrieve the associated silver from the previous smelting. At the time he used only one furnace. Months later he fired up a second one.
By the time Hardinge opened his smelter in 1892, Aspen was well positioned to support the operation. The furnace burned coke for fuel. By then, the city had connected by rail to the Cardiff coal mines and coke ovens up the Crystal River Valley. The smelters also needed a power source to drive the huge fans that whipped the burning coke to high temperatures. Hardinge's smelter lay just yards from Aspen's brand-new electric plant on Castle Creek — source of a third necessity: water.
Hardinge fired up his second furnace and began to process 60 tons of ore daily. He experimented with adjustments to accommodate Aspen's ore composition. About 30 employees shoveled ore and coal and operated the plant. They first shoveled three or four tons of charcoal into the furnace and fired it up with the air blowers. That took about four hours. Then they sealed the furnace and the temperature rose further. The heat melted a quantity of lead that had been left in the furnace and some old slag. When the system got hot enough to melt silver ore, workers shoveled in that precious ingredient. The molten material drained slowly — slag oozed into slag carts and silver slid like a twinkling stream into troughs.
Complications included keeping carbon monoxide from rapidly escaping the furnace and killing the workers. Where there is fire, carbon builds up. Hot air carried massive amounts of dust, harvested in large cotton filter bags as the air exited through openings in the ceiling of the "ash room." Tons of this dust recycled through the furnace weekly, each ton yielding up to 70 percent lead plus 36 ounces of silver.
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No matter how many mountains miners moved, ore car by ore car, profits depended on ore quality as much as quantity. During 1892, 15,000 tons of ore shipped from Aspen to Leadville and yielded 8.2 million ounces of silver. That's 550 ounces of silver per ton. In the same year Hardinge's smelter processed only 4,000 tons of ore for 120,000 ounces of silver, or 30 ounces per ton. Aspen's other smelter, The Holden, processed 30,000 tons of ore for 690,000 ounces of silver, a paltry 23 ounces per ton.
Even with the highest quality ore, profits rose and fell with prices. Hardinge worked for months to perfect his process. When he got it all working, the price of silver dropped, ore production fell off, and he closed up shop.
Leadville's operations continued as Aspen's first choice for smelting. Even so, the number of operations fell from 16 in 1879, to four during the 1890s, to two that survived the Panic of 1893. One outcome of that panic, repeal of the Sherman Silver Purchase Act, had decreased demand for silver. Smelters could make a stream of silver from solid ore. But they could not turn a government curse into a cash cow.
Tim Willoughby's family story parallels Aspen's. He began sharing folklore while teaching Aspen Country Day School and Colorado Mountain College. Now a tourist in his native town, he views it with historical perspective. Reach him at email@example.com.
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