Electrification, Demand Explosion and Mass Production: 1886-1967

As seen in figure 10, the electrification of the US, beginning with Edison’s Pearl Street power plant in New York City, in 1882, changed everything for copper. By 1930, less than 50 years later, 70% of US households were electrified. To meet skyrocketing demand, new production methods, such as block caving (orange bars), open pit mining (blue bars), froth flotation, and advances in smelting, like the Bessemer converter, coupled with continental-scale railroad transportation, allowed large deposits of lower grade ores to be exploited. Many of these new methods were either developed (block-caving at Ray) or first applied on a large scale (flotation at Inspiration) at mines in Southwestern North America.

Figure 10. Graphical history of copper mining in SW N America, with copper discoveries, price, production, technological advances

Open pit mining with steam shovels and railroad transport, was developed at Bingham in 1906, implemented at Santa Rita in 1910 (figure 10), Ajo in 1916 and Bisbee in 1917. The first use of froth flotation on a large scale at a copper mine was by Inspiration Copper in 1915, at its Miami, Arizona operation. Leaching has always been a part of copper production in Southwestern North America, due to the large tonnages of oxidized, soluble copper-bearing ores in the upper levels of most deposits, though recovery methods changed with time.

These techniques and technologies allowed lower and lower ore grades to be profitably exploited, even as real prices fell, due to increasing supply. Labor organization and strife with management followed, as did the usual cycles of boom and bust that accompanied wars, economic expansions and devastating contractions, like the Great Depression. From the 1910s through the early 1950s, discoveries of new deposits were few and far between, as industry efforts were focused on maximizing profits from known giant deposits.