Copper-bearing minerals are not only numerous, but widely though irregularly distributed. More than this, copper is found associated with many different metals and under varied conditions. Nevertheless but few copper-bearing minerals are important in the ores of this metal, and the number of important producing districts is comparatively small. Most of the copper ores now worked are of low grade, but can be profitably treated because of the extent of the operations and possibility of concentration. Occasionally low-grade ores are found which are self-fluxing, as those of the Boundary District of western Canada. The introduction of pyritic smelting has permitted the profitable treatment of low-grade pyritic-copper ores, even if they carry no gold or silver. Complex ores of copper, lead, and zinc sulfides are more costly to treat, but this expense may be more than made up for by their gold and silver contents. Sulfide ores of copper are almost invariably leached near the surface, except where the former surface material has been removed by rapid erosion or glaciation. Many copper ores, however, contain other metals that are not so easily leached as copper. As a result, many valuable deposits of copper sulfide ore have been discovered by downward exploitation of oxidized gold and silver ores. In regions where copper ores abound areas richly stained with iron are generally considered worthy of exploration in a search for copper. On the other hand, deposits of copper have been found below outcrops that show very little iron oxide. These outcrops, however, are generally silicified and kaolinized. Most of the large copper sulfide deposits in the United States show three zones a leached zone near the surface, an enriched zone below the leached zone, and a zone of lower-grade primary ore below the enriched zone. In the unaltered primary portion of the ore body the copper compounds are mainly sulfides, but arsenides and antimonides are also known. In the leached goethite gossan zone the copper occurs as carbonates, sulfates, silicates, oxides, native, and more rarely as phosphates, arsenates, antimonates and vanadates.

Copper can be extracted from its ore by: 1. Traditional mining underground sinking a vertical shaft into the Earth to an appropriate depth and driving horizontal tunnels into the ore. open pit 90% of ore is mined by this method. Ores near the surface can be quarried after removal of the surface layers. 2. Leaching The ore is treated with dilute sulphuric acid. This trickles slowly through the ore dissolving copper to form copper sulphate. The copper is recovered by electrolytic refining. Advantages of this process are: much less energy is use than in traditional mining no waste gases are given off it can be used on ores with as little as 0.1% copper - for this reason, leaching extraction is growing in importance.
What's in an ore?
	There are many types of copper ore found throughout the world. Picture 4 shows the distribution of these deposits. About 80% of all copper extracted comes from sulphide ores. A typical ore contains only 0.5% to 2.0% copper. It is a measure of the value of copper that it is worth extracting it from such small concentrations. The ore is a mixture of minerals and rock (called gangue). The most common copper minerals are: Mineral Formula Appearance % copper in  mineral Cuprite Cu2O Red, earthy see Qn 2 Chalcocite Cu2S Dark grey, metallic see Qn 2 Bornite Cu5FeS4 Golden brown, metallic 63 Malachite CuCO3Cu(OH)4 Bright green, earthy 58 Azurite 2CuCO3Cu(OH)4 Blue, glassy 55 Chalcopyrite CuFeS2 Golden yellow, metallic 35 The first step is to physically remove the gangue.

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