Chalcopyrite smelting

Copper. Copper is economically extracted by smelting of a chalcopyrite concentrate. A copper electrowinning process was developed commercially in 1912 for the treatment of lean ores. It is also suitable for treatment of copper oxide or sulfate obtained by roasting of the concentrate. 

Silver items, however, are also relatively rare in the archaeological record. The most common metal found is either copper, usually alloyed with either tin (bronze) or, in the later periods, zinc (brass), or iron. The latter contains very little lead and, because of severe corrosion problems, its survival rate is often low (but see Degryse et al., 2007). Fortunately, copper can also be characterized from its lead isotope signature, since the primary ore of copper is chalcopyrite (CuFeS2), which often co-occurs with galena (PbS) and sphalerite (ZnS). Even if the ore used is a secondary mineral formed by the oxidation of the primary deposit, the copper smelted from such a deposit would normally be expected to... 

Copper, too, can be recovered from copper sulfides without resort to a reductant such as coke. The concentrate usually contains iron sulfides (in fact, the most widely occurring ore of copper is CuFeS2, chalcopyrite), as well as silicates. The chemistry of copper smelting is subtle, but the commonly employed two-stage process can be summarized as follows ... 

A heat and material balance (based on 1000 kg of chalcopyrite) was created for the first furnace (Table III), smelting furnace (Table IV), and flash furnace (Table V) based upon thermodynamic calculations [6], Utilizing preheated air from a downstream process in the acid plant and 500 C particulate CuO, the reaction in the first furnace proceeds in a slightly exothermic fashion, yielding 800 °C products with excess heat that can be utilized to overcome heat losses. 

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