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Mining began in the period 1895–1900, and continued until shortly after World War I. Copper is present as chalcopyrite, occurring with magnetite, pyrite, garnet, epidote, diopside, and hornblende, in replacement deposits in greenstone. Gold and silver were recovered as byproducts. [13] Copper was discovered at Prince William Sound in 1897.
[1]: 306 Although the copper-mining region stretched about 100 miles from northeast to southwest, the most productive early mines, working fissure veins, were those at the north end in Keweenaw County (such as the Central, Cliff, and Phoenix mines), or at the south end in Ontonagon County (such as the Minesota Mine).
During World War II, government-mandated restrictions on the use of various metals halted production of all metal toys in favor of the war effort. Lionel, seeking an alternative product to keep the brand name alive during the war, sought the assistance of Samuel Gold, a designer of various novelties including cereal and soft drink premiums ...
A typical village war memorial to soldiers killed in World War I. National World War I Museum and Memorial in Kansas City, Missouri, is a memorial dedicated to all Americans who served in World War I. The Liberty Memorial was dedicated on 1 November 1921. [338]
On April 19, 1920, the Industrial Workers of the World (IWW) and the Metal Mine Workers Industrial Union called for a strike in the mines around Butte. They hoped the strike would help secure higher wages, an eight-hour day, and end the use of the rustling card, a system that allowed employers to blacklist employees involved in union organizing, among other goals. [1]
The Granite Mountain/Speculator Mine disaster of June 8, 1917, occurred as a result of a fire in a copper mine, and was the most deadly event in underground hard rock mining in United States history. Most men died of suffocation underground as the fire consumed their oxygen; a total of 168 miners were killed.
A combination of low copper prices, depleted mines, competition from newer and richer mines, and continuing labor troubles eventually closed all of the Copper Country Mines. While the Quincy Mine had already shut down in 1931, it was reactivated in 1937 due to World War II-era demand for copper; however, it shut down permanently in 1945. [12]
Heavy copper layers are used for high current or to help dissipate heat. [citation needed] On the common FR-4 substrates, 1 oz copper per ft 2 (35 μm) is the most common thickness; 2 oz (70 μm) and 0.5 oz (17.5 μm) thickness is often an option. Less common are 12 and 105 μm, 9 μm is sometimes available on some substrates.