Last Stamp Standing
During the Copper Empire’s peak, over 100 steam stamps were in operation across the peninsula. As mines and their mills succumbed, these massive stamps were quickly sold or scrapped for quick cash. With the arrival of the Second World War any remaining stamps were quickly drafted into the war effort - providing much needed steel and iron for military equipment. By the end of the empire in the 60’s, stamps had become and endangered species. Today only one has managed to survive.
Anatomy of a Mill (Stamps)
The processes of mill work can be separated into four distinct stages. The first stage involves breaking down the copper bearing rock from the mill into small pieces - a process known as stamping. These small particles of rock are then passed onto a series of roughing jigs followed by a series of refining jigs. In the last stage the remaining rock is sent to the wash floor, where a series of slime tables are used to remove the last traces of copper from the rocks before being discarded. We start today with the first and most important step of the entire process: the stamps.
Anatomy of a Mill (Rock Bins)
The first stop for any rock entering a Copper Country stamp mill is one of several large storage bins that sit up and behind the mill’s stamp batteries. Since the rock will be transported through the mill primarily by gravity, these bins sit at the highest point of the mill complex. These bins are fed from overhead via an elevated trestle, from which rock cars empty their loads between the rails and down into the bins.
Anatomy of a Mill (p1)
In the beginning of the Copper Empire, very little importance was put on milling. It was the mines themselves that produced copper, usually in the form of large pieces known as mass (or barrel) copper. These large pieces required no milling, and fetched high prices out east. Milling at that time was considered only a secondary producer of copper for a mine, relegated to simply processing a mine’s left-overs. The small amount of copper that would be recovered would often barely cover the operating costs of the mill itself.
Keweenaw Sands (p3)
The steam stamp technology that helped propel an industry into profitable territory required large amounts of water to function - somewhere in the vicinity of millions of gallons a day. This forced more modern mines to place their mills near the only sources of water large enough to supply these numbers - Torch Lake, Portage Lake, and Lake Superior. But this wasn’t the case a generation earlier, when a mill’s gravity stamps required only a fraction of those water needs. Because of this mills could be located along rivers, streams, or even small man-made lakes. These “inland mills” as they are often called were done away with by the turn of the century, but many of these mills can still be located by the stamp sands they left behind.