Copper and molybdenum resources were not recognized as valuable commodities until economic needs demanded the collection and processing of these minerals in large amounts. The most expansive deposits of copper and molybdenum occur in massive low grade ores and are found in intrusive porphyry formations, although many smaller sized but higher grade ores are located in non-porphyry areas. The nation has abundant domestic copper ore reserves but because of many detrimental economic factors much of the copper used by the U.S. industry is imported. Molybdenum ore is profuse and exports of it are high to fulfill the needs of foreign demand.
Copper was first used by people around 4000 B.C. in the manufacture of tools because of its malleability and later became an important additive in harder, more useful metals such as bronze (copper+tin; 2500 B.C.) and brass (copper+zinc; 0 A.D.). The growth of copper production in the United States has been a relatively recent occurrence.
Porphyry Lion
Open Pit Mines, Southern Arizona 2010-01-14 IISS02...
Climax mine near Leadville, ColoradoNorth American French explorers knew of sources of native copper in the region of Lake Superior and the area natives had copper jewelry and ornamentation. Earnest copper mining began in Simsbury, Connecticut about 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...