Copper

A ductile, malleable metallic element used in many functional and decorative artifacts. It was one of the first metals to be exploited by man because, like gold, it can be found in the native form, pure and requiring no smelting. It is most frequently obtained from a variety of ores: the carbonate (malachite), oxides, and sulphides. Shaping could be done by simple hammering, which served also to harden the metal. 'Pure' copper may contain up to one per cent of impurities and the concentrations of these impurities may indicate the source of the ore. Arsenical copper alloys (2-3% arsenic) have some advantages over pure copper in ease of casting and in the hardness of a hammered edge. In the New World, cire perdue casting of copper is first recorded in the Paracas culture of Peru and by the European conquest, the technique was practiced from the southwest U.S. to Argentina. Copper occurs fairly widely in the Old World, and was first used in Western Asia before 8000 BC as a substitute for stone, though it did not come into common use until after 4000 BC. Metallurgy dawned in Egypt as copper was cast to shape in molds (c 4000 BC), was reduced to metal from ores with fire and charcoal, and was intentionally alloyed with tin as bronze (c 3500 BC). The earliest surviving examples from Egypt are small artifacts such as beads and borers of the Badarian period, c 5500-4000 BC. Great copper hoards occur in the Ganges-Yamuna alluvial plain and just south of the lower Ganges, and elsewhere in India and Pakistan.

A relatively soft metal, which can be cold worked and melts at a low enough temperature to be cast using the technology available in antiquity. The metal occurs, rarely, as nuggets of native copper; it is in this form that it was first worked by man. More frequently, copper is obtained from ores. These are quite widely found, and may be oxide ores (including malachite) or sulphide ores. Smelting of these ores can be accomplished in a simple furnace, assisted by bellows. The oxide ores involve the least complicated smelting process. The resulting copper ingot could be cold worked or remelted and cast in a mould. ‘Pure’ copper may contain up to one per cent of impurities. The concentrations of these impurities may indicate the source of the ore. The metal is said to be an alloy when it contains more than one per cent of another element. Tin bronze thus contains more than one per cent tin. European Early Bronze Age copper-based artefacts may also contain quantities of arsenic. These fall into two groups. Those with one per cent or less arsenic are classed as ‘pure’ copper. Others, which commonly have two or three per cent arsenic (sometimes as much as seven per cent) can be classed as arsenical copper alloys. These may come from an ore body particularly rich in arsenic or may be deliberate alloys. Arsenical copper alloys have some advantages over pure copper in ease of casting and in the hardness of a hammered edge. Copper occurs fairly widely in the Old World, and was first used in Western Asia before 6000 be, though it did not come into common use until after 4000 be. It was also used by prehistoric communities in the New World, both in the Arctic area and in South America.