| A History of Mining in Arizona | Copper: The Star of Arizona | Copper: An Economic Profile | Mine To Market | ||
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  From Mine to MarketCopper Mining, the profitable extraction and production of copper, is one of man's oldest commercial activities. This illustrates the series of steps associated with the mining and processing of copper ore. Exploration & DiscoveryCopper mining begins with a team of scientists, including exploration geologists, geochemists, geophysicists, metallurgists and engineers discovering a copper ore deposit — a concentration of copper minerals that can be mined profitably. Mining (Underground)Underground mining is used when copper ore lies deep beneath the earth's surface. First, the miners drive (excavate) an opening into the earth's surface. A vertical opening is called a shaft. A passage that is nearly horizontal, dug into the side of a hill or mountain, is called an adit. From these main passages, miners develop systems of horizontal passages called levels. Mining (Open Pit)Open pit mining is used to extract massive amounts of low grade copper ore that are at or near the surface of the earth. An open pit mine has the appearance of a series of benches or terraces. The mining process starts with heavy earth-moving equipment (dozers, scrapers, electric shovels and trucks) removing any overlying dirt or rock (overburden) that is present. Milling & ConcentratingFrom the mine, copper ore, containing copper-sulfide minerals, is crushed and ground to a size suitable for recovery of the copper mineral. The copper mineral is recovered and concentrated by a process called flotation. In flotation, the finely ground ore is mixed with water to from a slurry. Certain chemicals or reagents that coat only the desired copper minerals are added in small amounts. Rising air bubbles capture the coated mineral particles and float them to the surface where they are skimmed off and dried. This dried material is called copper concentrate and is approximately 30 percent copper, 27 percent iron and 33 percent sulfur. The waste rock, now called tailings remain in the slurry. Leaching and ElectrowinningFrom the mine, leachable ore (containing copper-oxide minerals) is placed directly on lined leach pads where a weak acid solution is sprayed on the surface of the heap. This solution percolates down through the pile of ore and dissolves the acid-soluble sopper. The copper bearing solutions are collected and pumped to a solvent extraction plant where organic chemicals remove the copper from the solution. The resulting electrolyte solution is transferred to the electrowinning process where copper is plated out as a 99.99% pure copper cathode. SmelterCopper concentrate is fed to a series of furnaces where non-copper elements are burned off or separated. This purifying process results, successively, in matte, blister and finally, 99 percent pure copper. The molten copper is poured in molds called anodes. ElectrorefiningThe 99% pure copper anodes are immersed in an acid bath where the pure copper is transferred from the anodes at the positive pole of an electric circuit to cathodes at the negative pole. The result is a 99.99+ percent pure copper cathode that weighs approximately 200 pounds. FabricationCathodes of 99.99+ percent pure copper are shipped as melting stock to mills or foundries. They are also often cast into wire rod, billets, cakes, or ingots which are later used in the production of products we use every day. |
Copyright © 2006 Arizona Mining Association. All rights reserved.