Copper And Molybdenum Deposits In The United States

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1709 and copper was actually exported to England after a
source was discovered in New Jersey around 1719. In later times domestic copper
resources did not satisfy national needs until the discovery of gold in
California shifted the focus of mineral exploration westward and strikes of rich
copper ores occurred in Tennessee and the Cordilleran base regions. The Civil
War caused copper demand to increase greatly in order to manufacture cartridges
and canned goods, this resulted in the openings of numerous copper mines of
which more than 90% were in the Lake Superior area giving an important advantage
to the Union armies. Major copper production districts then shifted to Montana
and Arizona in the early 1890's. Production increased to reach peak levels of
900,000 tons a year during World War I and in 1970 1,600,000 tons of copper were
produced but recent levels are lower, fluctuating between 1-1.5 million tons a
year. Technology has aided in increasing production efficiency wich ...

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in hydrothermally altered
intrusives with closely spaced phenocrysts in a microaplitic quartz-feldspar.
The intrusive ranges in age from the Mesozoic to the Cenozoic and in composition
from tonalite to granite. Ore is found in stockwork veinlets and random grains
in the intrusive and surrounding fractures. The ore includes chalcopyrite,
pyrite, and sometimes molybdenite, magnetite, and gold. Green and blue copper
carbonates and silicates developed into weathered outcrops overlying enriched
zones containing chalcocite and other sulfides. There are 31 U.S. porphyry
copper locations with an average grade of .54% copper ranging from a low of .31%
to a high of .94%.
Another type of ...

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