Cornish-style gravity stamps and copper washroom launders remained the standard in the Lake Superior copper district for about a decade. While gravity stamps accomplished their intended purpose, the introduction of the steam-powered stamp revolutionized milling in the region.

In 1853, the Hill Mine, set off from the Copper Falls Mine, constructed a stamp mill equipped with 24 stamp heads, with a steam engine powerful enough to drive an additional 24, according to the Annual Report of the Commissioner of Mineral Statistics of Michigan for 1880. About the same time, improvements were made to the mill at the Cliff Mine, where 24 stamp heads were used, to which another 12 were added. The old stamp mill at the Phoenix Mine drove eight gravity stamps, but was increased to 24 in 1855, operated by water power. Around 1859, the company abandoned this underpowered mill, introduced a steam engine, and erected a new mill containing 48 stamps. The engine selected was of sufficient power to operate 100 stamps.

The Pewabic Mining Company was organized in 1854. When the company built its mill on the shore of Portage Lake in 1856, its directors did not build a large mill with 12, 24 or 48 stamps to process their amygdaloid copper rock. Their mill contained just two stamps. But these stamps were new to the copper region. William Ball had patented his steam-powered stamp on May 27, 1856. They were steam-powered stamps, knowns as Ball’s stamps. They were far more powerful and faster than drop stamps and far more efficient.

As described by 911 metallurgy, the steam stamp “consists of a direct-acting vertical engine, having a steam cylinder and slide valve at the top, the piston-rod being rigidly connected with the stamp.” Comparisons between the efficiency of drop stamps and this new steam stamp demonstrate the Pewabic’s decision to adopt the brand-new technology.

The Mineral Commissioner’s report for 1880 reported that during trials of its stamp mill in 1858, the Phoenix company found that “the speed attained by the stamps was 48 strokes per minute.”

With Ball’s steam stamps, 911metallurgy reported, their speed averaged 90 to 100 blows per minute, and the out-put is from 100 tons to as much as 225 tons of ore per head in twenty- four hours.

“As their capacity is so great their use is limited to cases in which large quantities of ore are available,” the mining engineering website states, “one Ball steam stamp, such as is used in the Lake Superior district, being equal to at least fifty head of gravitation stamps.”

Appletons’ cyclopaedia [sic] of applied mechanics, vol. 2, published in 1880, included the Pewabic stamp mill in a comparative study, which it mentioned on page 792:

“Three Ball’s stamps at the Pewabic mill, Lake Superior, running from Jan. 1 to Dec. 31, 1875, gave the following results: No. of days running, 281 3/4; tons of rock stamped, 58,942; tons stamped per cord of wood, average 10.84; total running expenses, $46,208.37; cost of stamping and washing one ton of rock, $0.79.”

Part of the Michigan Geological Survey Division’s Keweenaw Series of Michigan, Issue 6, Part 2, published in 1911, stated that:

“These stamps were nothing more than steam hammers but the stroke was made regular by having the valves to the steam cylinder operated by an independent engine.”

Ely Whitney Blake’s invention of the mechanical rock crusher, or breaker, was another revolutionary innovation that first appeared in the district around 1863. Crushing mine rock mechanically not only exponentially reduced the time consumed by breaking it by calcining, it also dramatically reduced labor, freeing those men to do other jobs.

Another invention that revolutionized copper milling was something called the Collom Jig, an invention of John Collom, who was an engineer at the Huron Mine. The jig is what C. Harry Benedict described in his book “Red Metal: The Calumet and Hecla Story,” as the first mechanical jigger. A jigger is a type of gravity concentrator that separates materials of different densities. In the case of Lake Superior copper, it separated small particles of copper from rock.

As explained by the Keweenaw Series of Michigan report, the crushed copper-bearing rock was mixed with high volumes of water to spread out over a wire screen, through which a pulsating stream of water flowed. The pulsating water kept the rock and copper particles in motion, while the heavier particles (copper) settled into a catch box, or settling box, below the screen.

After passing through the Collom Jig, the “slime” next went to another local invention of Atlantic Mine engineer, William Evans, which was the Evans Slime Table. This was a rotating table that also relied on high volumes of water to further separate and treat the slime from the jig.

The separator created two classes of product, explained Charles M. Rolker in his presentation, “The Allouez Mine and Ore Dressing, as Practiced in the Lake Superior Copper District.” The products were called heads and tails.

Rolker’s presentation, which was printed in the Proceedings of the Annual Meeting of the Lake Superior Mining Institute, Vol. 2, in 1894. By then, many advancements, innovations and refinements had been made to the Lake Superior milling practice:

Steam stamps had been introduced in 1856; mechanical Blake jaw crushers appeared in the mid-1860s, which replaced calcining; both new technologies greatly reduced the time and labor of mineral concentrating. The Evans Slime Table and the Collom Jig increased the efficiency of processing (somewhat), replacing the old copper washroom floors. These were were all developments that were quickly adopted, tweaked, and put into use all across the copper region. By the turn of the 20th century, the Lake Superior copper region was ideally set up to contribute immensely to Allied war effort of 1914-1918 and beyond.