Metallurgy in pre-Columbian America is the extraction, purification and alloying of metals and metal crafting by Indigenous peoples of the Americas prior to European contact in the late 15th century. Indigenous Americans had been using native metals from ancient times, with recent finds of gold artifacts in the Andean region dated to 2155–1936 BCE, and North American copper finds being dated to approximately 5000 BCE. The metal would have been found in nature without the need for smelting, and shaped into the desired form using hot and cold hammering without chemical alteration or alloying. To date "no one has found evidence that points to the use of melting, smelting and casting in prehistoric eastern North America."
In South America the case is quite different. Indigenous South Americans had full metallurgy with smelting and various metals being purposely alloyed. Metallurgy in Mesoamerica and western Mexico may have developed following contact with South America through Ecuadorian marine traders.
South America
South American metal working seems to have developed in the Andean region of modern Peru, Bolivia, Ecuador, Chile, and Argentina with gold and native copper being hammered and shaped into intricate objects, particularly ornaments. Recent finds date the earliest gold work to 2155–1936 BCE. and the earliest copper work to 1432–1132 BCE. Ice core studies in Bolivia however suggest copper smelting may have begun as early as 700 BCE, over 2700 years ago. By 1410–1090 BCE, gilding was practiced in coastal Peru. Further evidence for this type of metal work comes from the sites at Waywaka (near Andahuaylas in southern Peru), Chavín and Kotosh, and it seems to have been spread throughout Andean societies by the Early horizon (1000–200 BCE).
Unlike other metallurgy traditions where metals gained importance through practical use in weaponry and everyday utensils, metals in South America (and later Central America) were mainly valued as adornments and status objects. Though also functional objects were produced, even in the metallurgically advanced Andean cultures of the Inca era stone tools were never completely replaced by bronze items in everyday life. During the Early horizon, advances in metal working produced spectacular and characteristic Andean gold objects made by the joining of smaller metal sheets, and also gold-silver alloy appeared.
Two traditions seem to have developed alongside each other – one in northern Peru and Ecuador, and another in the Altiplano region of southern Peru, Bolivia and Chile. There is evidence for smelting of copper sulphide in the Altiplano region around the Early horizon. Evidence for this comes from copper slag recovered at several sites, with the ore itself possibly coming from the south Chilean-Bolivian border. Near Puma Punku, Bolivia, and at three additional sites in Peru and Bolivia, portable smelting kilns were used to cast I-shaped "cramps" (fasteners) in place, to join large stone blocks during construction. Their chemical analysis shows
The estimated date of these pours lies between 800 and 500 BCE.
Evidence for fully developed smelting, however, only appears with the Moche culture (northern coast, 200 BCE – 600 CE). The ores were extracted from shallow deposits in the Andean foothills. They were probably smelted nearby, as pictorially depicted on the metal artifacts themselves and on ceramic vessels. Smelting was done in adobe brick furnaces with at least three blow pipes to provide the air flow needed to reach the high temperatures. The resulting ingots would then have been moved to coastal centers for shaping in specialised workshops. Two workshops found and studied near the administrative sections of their towns, again showing the prestige of metal. Analysis of a Moche statue composed of numerous thin metal layers revealed complex plating and gilding involving a combination of immersion in acidic solutions and the application of extreme heat.