|Principal Copper-bearing Minerals|
Today the most common source of copper ore is the mineral chalcopyrite. About 50% of all copper produced world wide is extracted from this ore. Historic mine extracted high grade ores, where copper minerals were contained as pure as possible. Unfortunately those mines are general polymetallic hydrothermal dykes, which are in general rather thin and surrounded by hard rocks. As long as they were mined manually this was rather positive, as the mines were stable. But they are not very good for modern mining using heavy machinery. So modern mines generally used massive deposits of huge size but low grade. They are often mined in huge open cast mines with very heavy machinery.
There are various processes for the extraction of the metal. The most simple and cheap one is the use of sulfuric acid for leaching the copper, called solvent extraction. The soluted copper in the acid is later solidified by the electrowinning technology. This process works only with oxide ores, as sulfides are resistant to sulfuric leaching. Sulfides are concentrated using froth flotation and are subsequently smelted to recover the copper. There is also the possibilty to use a bacterial oxidation process to oxidize the sulfides. Then the upper leaching process can be used.
A rather elegant method is the electrorefining, where the copper is refined by electrolysis. Processed blister copper is placed in an aqueous solution of 3-4% copper sulfate and 10-16% sulfuric acid. Cathodes of thin rolled sheets of highly pure copper are used to accumulate the copper from the ore.