People in the Americas have been using native metal from very early times, with recent finds of gold artefacts in the Andean region dated to 2155 - 1936 B.C. () and North American copper finds dated to approximately 5000 B.C. e.g. (). The metal would have been found in nature without need for smelting techniques and shaped into the desired form using heat and cold hammering techniques without chemically altering the metal by alloying it. 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. This early familiarity with metals then developed into full metallurgy with smelting and various metals being purposefully alloyed. Metallurgy in Mesoamerica developed from contacts with South America, as such the largest section of this entry will be dedicated to it.
South American metal working seems to have developed in the Andean regions of modern Peru and Bolivia with gold being hammered and shaped into intricate objects, particularly ornaments (), recent finds dating the earliest metal work to 2 155 to 1936 B.C. (). It was found in the context of a society undergoing social and economic changes but still very much small food producer and not quite sedentary yet. Which breaks away from the idea that this type of metal work developed in societies with enough food surplus to support an elite. Rather than being a product of a hierarchical society gold might have been meshed in the creation of it. Further evidence for this type of metal work comes from the sites at Waywaka, Chavin and Kotosh (), and it seems to have been spread throughout Andean societies by the Early horizon (1000 - 200 B.C.)
Unlike in other metallurgy traditions where metals gain importance due to their widespread use from weaponry to every day utensils, metals in South America (and latter in central america) were mainly valued as adornments and objects representative of a high status (this not to say that some more functional objects were not being produced). It is during the Early horizon that advancements in metal working result in spectacular and characteristically Andean gold objects made by the joining of smaller metal sheets and also gold-silver alloy appears.
Two traditions seem have developed along side each other, one in northern Peru and Ecuador 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).
Evidence for fully developed smelting however only appears with the Moche culture (northern coast, 200 B.C. - 600 A.D.). The ores were being extracted at shallow deposits in the Andean foothill, whether by specialised workers or slaves/prisoners is unclear. In any case the ores are believed to have been smelted at nearby locations, evidenced in the actual metal artefacts and from ceramic vessels depicting the process, which is believed to have been occurring in adobe brick furnaces with at least 3 blow pipes to provide the air flow needed to reach the high temperatures. The resulting ingots would then have been moved to coastal centres where shaping of the object would occur in specialised workshops. Both of the workshops found and studied were located near administrative sections of the respective towns - again indicative of the high value placed upon metal.
The objects themselves were still mainly adornments, now often being attached to beads, with some functional objects being fashioned but since these were so elaborately decorated and often found within high status burial contexts that it still believed that they were still being used for more symbolic purposes. The appearance of gold or silver seems to have been important with a high number of gilded or silvered objects as well as the appearance of Tumbaga, a copper/gold and sometimes also silver alloy. Arsenic bronze was also being smelted from sulphidic ores, a practice either independently developed or learned from the southern tradition.
There is a gradual spread north into Colombia, Panama and Costa Rica reaching Guatemala and Belize by A.D. 800.
It is really only with the Incas that metals gain a more utilitarian use, nonetheless it remained a material through which to display wealth and status. The characteristic importance placed on colour, which had led to some of the earlier developments was still present (Sun/Moon association with gold/silver). Metal other than gold had also an intrinsic value with the axe pieces being of particular note in this regard. With the spread of metal tools being championed by the Incas it is thought possible that a more Old World use of metals would have become more common. In any case ‘Bronze can be seen as an expensive substitute for the equally efficient stone’ ( pp 183) and why waste the gift of the Gods then?
Metallurgy only appears in Mesoamerica in A.D. 800 with the best evidence from West Mexico. Much like in South American it was seen as a material for the elite and it was the special qualities of colour and resonance that seemed to have appealed most and then led to the particular technological developments seen in the region ().
Exchange of ideas and goods with peoples from today’s region of Ecuador and Colombia (likely via a maritime route) seems to have fueled early interest and development. Similar metal artefact types are found in West Mexico and the two regions: copper rings, needles and tweezers being fabricated in the same ways as in Ecuador and also found in similar archaeological contexts. There is also a multitude of bells found , but in this case having been cast using the same lost-wax casting method as seen in Colombia (). At this period copper was being used almost exclusively.
Continual contact kept the flow of ideas from that same region and latter, coinciding with the development of Andean long distance maritime trade, influence from further south seems to have reached the region and lead to a second period (A.D. 1200-1300 to the Spanish arrival) (). By this time copper alloys were being explored by West Mexican metallurgists some because the different mechanical properties were needed to fashion specific artefacts like particularly axe monies - further evidence for contact with the Andean region - but in general developed the new properties such alloys introduced to match their own regional representations - specially wirework bells which at times had such high tin content in the bronze that it was irrelevant for its’ mechanical properties, but gave it a golden colour.
Although the actual artefacts and then techniques were imported from the south the ores being worked by west Mexican metallurgists were from the abundant local deposits, the metal was not being imported. Even when the technology spreads from West into north-eastern, central and southern Mexico artefacts that can be traced back to West Mexican ores are if not exclusive, at least abundant. (It is not always clear if the metal reached its’ final destination as an ingot, an ore or a finished artefact). Provenance studies on metal artefacts from southern mesoamerica cast with the lost-wax technique and dissimilar to west Mexican artefacts have shown that there might have been a second point of emergence of metallurgy into mesoamerica there since no known source could be identified. ()
The Aztecs did not initially adopt metal working (even if they had acquired metal objects) however as conquest gained them metal working regions the technology started to spread and by the time of the Spanish conquest a blooming bronze smelting technology seemed to be nascent.
‘In North American, north of the Rio Grande, indigenous cultures did not smelt, melt, or alloy metals relying instead on the relative abundance of native copper’ ( pp 26)
As widely accepted as this statement might be it should not be considered synonymous with a lack of metal objects, as it points out native copper was abundant particular in the Great Lakes region and ‘overlooks the simple fact that there was really very little to be gained by smelting (...) (Martin 1999). The latest glacial period had resulted in the scouring of copper bearing rocks with once the ice retreated were readily available for use in a variety of sizes (). This has led to copper being used shaped via cold hammering into objects from very early dates (Archaic period in the Great Lakes region: 8000-1000 B.C.) and actual mining of copper veins(Old Copper Complex). There is considerable argument over the dates for evidence of actual mining. ().
Unlike their more Southern counterparts North American metallurgy had a more utilitarian purpose from very early on, with losing sight of the prestige attached to the metal artifacts (knifes, fishhooks, bracelets).
Extraction would have been extremely difficult. Hammerstones could have been to break off small enough pieces to be worked. It is also possible that this no doubt labor intensive process could have been eased by creating fires on top f the deposit until the rock was very hot and then quickly dousing it with water and thus creating small cracks, and then repeated to create more small cracks.
The copper could then be cold-hammered into shape, which would make it brittle, or hammered and heated in an annealing process to avoid this. The final object would then have to be grounded and sharpened using local sandstone. Numerous bars have also been found, possibly indicative of trade for which their shaping into a bar would also serve as proof of quality.
With Great Lake artifacts found in the Eastern Woodlands of North America there seems to be an indication for widespread trading networks by 1000 B.C. Progressively the usage of copper for tools decreases with more jewelery and adornments being found. This is believed to be indicative of social changes to a more hierarchical society. ()
However this Great Lake model as a unique source of copper and of copper technologies remaining somewhat static for over 6000 years has recently come into some level of criticism, particularly since other deposits seem to have been available to ancient North Americans, even if a lot smaller. () and ()
Northeastern North America: evidence from instrumental neutron activation analysis, Journal of Archaeological Science, 34(4), pp. 572–87.