Electrical innovation increases efficiency as lodes dwindle

Graham Jaehnig

By 1900, the Calumet and Hecla Mining Company had become one of the most complex non-ferrous metal mining plants in the United States. It had been built upon the single richest copper lode in the United States, east of the Mississippi River and was wealthy enough to satisfy its stockholders, provide for its workers and their families, and invest in its own sustainability.

By the turn of the century, diamond drilling, mining, milling and other reports all indicated that the copper content of Calumet Conglomerate Lode was gradually decreasing, particularly on the Hecla branch. Since 1867, when the Calumet and the Hecla companies were organized, they exploited the richest section of the lode, which was some two miles long. Deep-shaft, hard-rock mines, such as those throughout the Lake Superior copper district, sooner or later faced two unavoidable challenges: first, mining costs increased the deeper the mines were developed, and second, as the mines went deeper, the copper content of the rock steadily decreased. In terms of business, declining mineral content and increased mining costs translated into less copper being produced for market as production costs increased. Pittsburgh and Boston Mining Company’s once world-renowned Cliff Mine suspended operations in 1870 because the fissure vein upon which it mined had become exhausted. In 1898, the Central Mine shut down for the same reason.

Company President Alexander Agassiz, however, was aware that even once the Hecla branch was abandoned, its years of production were not directly over. Agassiz was a mining engineer whose talent for mining exceeded his education. He was keenly aware that 19th century milling technology was only 75% efficient. The rock stamps of the time, and the washing machines that separated the copper particles from the crushed rock, were capable of liberating only 75% of the copper in the stamped sand. The remaining 25% was simply washed out with the waste sands and left to pile up around the mill property. Enough stamp sand had been created that when it was deposited in Torch Lake, as a place to get rid of it, its accumulation had literally redrawn the shoreline.

C&H had always been more than thorough in its approach to mining and mineral production. According to a 1923 publication, Calumet and Hecla Mining Company, prepared by Edward B. Smith & Co. of the New York Stock Exchange, continuous assays were systematically taken during the years the sands were deposited. From studying the assay reports, it was estimated that the sands contained an accumulated average of 14.5 pounds of copper per ton.

Measurements of the tonnage of the piles indicated that approximate 40 million tons, of which 30 million tons was estimated to be recoverable, had accumulated. The publication went on state that in addition to the tailings piled around the Calumet stamp mill and the Hecla mill, C&H also owned the tailings from the Tamarack Mining Company’s mill, about a mile away from C&H’s mills. These sands were estimated to contain 12 pounds of copper per ton, of which approximately 9.25 pounds were recoverable.

The more immediate task was to improve the concentrating process to reduce the amount of copper washed away in the tailings.

The project of modernizing the mill locations on Torch Lake began in 1896. The Summary of Operations of the Calumet and Hecla Mining Company for that year reported that the “Electric Light Plant House” at the mills was completed and fully equipped. The report stated that the mills were now thoroughly lighted, along with the larger buildings, including the pump houses, wheel houses and warehouse.

The Summary of Operations for 1898 reported further expansion of operations on Torch Lake, when the summary stated that the foundation had been laid for another coal dock of 100,000-ton capacity, while the company’s work on constructing a canal from Bootjack Bay to Toch Lake, with a depth of 20 feet and a base of 90 feet along its entire length, “enabling us to bring the largest vessels navigating the lakes to our docks.”

The report went on to state that: “We are now continuing at the Mills our experiments relating to greater economy in stamping and washing our rock and in treating our mineral product.”

A laboratory for checking experiments relating to the efficiency of the stamps, and mineral content of the tailings, was constructed in Lake Linden. During the period of 1899-1900, an extension of the Hecla Mill was begun for the stamping of 2,500 tons of rock from the amygdaloid mine.

The summary for 1900 stated: “The experiments which have been making at the mills, with a view of diminishing the loss of copper carried off in the waste sands, have resulted in equipping one of the (stamp) heads with washing machines differing from those generally in use in the Lake Superior district.” Unfortunately, Agassiz did not disclose the machines he mentioned in the report.

What the report did include, however, was the statement that the company made a contract for the erection of a 60-foot sand wheel house, and an additional pump for the Hecla amygdaloid mill. A contract was signed with the General Electric Company for the machinery to “run part of the mill by electricity.” The next year, the house for the sand wheel was erected by the American Bridge Company, and the parts of the wheel had been delivered to the site.

The electric power house to drive the mill – and the sand wheel – had been erected and the foundations were ready for the main driving engine, as well as the generators and motors for the sand wheel and mill additions.

Agassiz reported in 1903 that the sand wheel, once in operation, was sufficient to “distribute the waste from 18 (stamp) heads to a distance of 2,800 feet from the mills.” The wheel was driven by a 700-horsepower electric motor.

While six additional stamps in the Hecla Mill extension were now operating, Agassiz stated that the washing machinery as well as the Chile Mills used for regrinding were driven by electric motors and “The equipment of this new mill is most satisfactory.”

It showed, he reported, an important cost reduction of stamping, as well as a reduction in copper being washed away with the tailings. While all the modifications made at the Torch Lake mill site reduced cost and mineral waste, they still did not address the topic of reclaiming the copper contained in the mill tailings. And while they achieved the desired effect of reducing mineral loss, they did not increase the amount of copper contained in the rock coming from the mines to the mill.

During the fiscal year of the company, ending on Apr. 30, 1904, reports stated that the new openings in the boundaries of the Red Jacket Shaft showed a decrease of about 15 percent in copper content from previous years.

As if more indication of the Conglomerate Lode’s gradual depletion of mineral content was needed for the company’s stockholders, Agassiz also reported that during 1903, all work of exploration in the area of the Hecla No. 12 Shaft (the most southerly opening), had been abandoned and removal of the pillars of the No. 11 Hecla Shaft were being removed, because no ground of any value had been located for development in the deepest extension of that shaft. Two years later, the removal of pillars in the areas of Nos. 2 and 3 Shafts of the Hecla Mine had begun.

In the face of the impending exhaustion of the Calumet Conglomerate Lode, C&H began to take steps to prolong its life as an active mining company. The stockholders, at their 1905 annual meeting, voted to authorize the directors to purchase stock in other companies, even in those no longer operating. The vote came after recent Michigan legislation permitting Michigan mining companies to invest themselves in other companies, providing for “a simple and effective method for the rapid development of the mineral lands of the Upper Peninsula; lands, many of which have remained underdeveloped for want of capital from the earliest date of copper mining in the state.”

While the Calumet Conglomerate Lode was, indeed, getting a bit tired, it was nearly to the point of total abandonment. But when that day was to come, the Board of Directors would already have other mining operations in place to make up for it. Among those operations would come the installation of technology needed to reclaim the copper bound up in the mill tailings.


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