Metallurgy in pre-Columbian America

Only with the Incas would metals really come into practical use. At Machu Picchu and other sites, metal was used for bolas, plum bobs, chisels, gravers, pry bars, tweezers, needles, plates, fish hooks, spatulas, ladles, knives (tumi), bells, breast plates, lime spoons, mace heads, ear spools, bowls, cloak pins (tupus), axes, and foot plow adzes.[21] Nonetheless, they remained materials 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). Metals other than gold also had an intrinsic value, with axe pieces being of particular note in this regard. With the spread of metal tools by the Incas, it is thought possible that a more Old World use of metals would have become more common. In any case, as Bruhns notes, "Bronze can be seen as an expensive substitute for the equally efficient stone."[9]^(p 183) However, sediment research in Bolivia has revealed that metals such as silver were smelted on a very large scale, thousands of tons, from late Tiwanaku to Inca times (1000–1530 CE), which suggests that the paucity of metal (particularly precious metal) at Inca sites is more likely caused by Spanish acquisition and export than by limited pre-colonial use.[22]

It has been claimed that the Inca Empire expanded into Diaguita lands in what is now north-central Chile because of its mineral wealth, but that view is rejected by some scholars.[23] Further, an additional possibility is that the Incas invaded the relatively well-populated Eastern Diaguita valleys (present-day Argentina) to obtain labor to send to Chilean mining districts.[23] The Incas influenced Diaguitas, who adopted Incan metalworking techniques.[24]

Farther south in Chile, Mapuche tribes within or near the Incan Empire paid tributes in gold.[25] Incan yanakuna are believed by archaeologists Tom Dillehay and Américo Gordon to have extracted gold south of the Incan frontier in free Mapuche territory. Following that thought, the main motive for Incan expansion into Mapuche territory would have been to access gold mines.[26] Among the Mapuche people of central and south-central Chile, gold had an important cultural significance that predates Inca contact.[25] At the time of the Spanish conquest of Chile, Mapuches are reported by various chroniclers to use gold ornaments.[25] According to historian Osvaldo Silva gold ornaments of the Mapuche of the Concepción area evidence some kind of interaction between the Mapuche and the Inca that may have been trade, gifts, or spoils of war taken from a defeated Inca army.[27] Pre-Hispanic Mapuche tools are known to have been relatively simple and made of wood and stone, but a few of them were actually made of copper and bronze.[28][29]

Iron was never smelted by Native Americans, thus the New World never entered a proper "Iron Age" before European discovery, and the term is not used of the Americas. But there was limited use of native (unsmelted) iron ore, from magnetite, iron pyrite and ilmenite (iron–titanium), especially in the Andes (Chavin and Moche cultures) and Mesoamerica, after 900 BCE and until c. 500 CE. Various forms of iron ore were mined,[30] drilled and highly polished. There is considerable evidence that this technology, its raw materials and end products were widely traded in Mesoamerica throughout the Formative era (2000–200 BCE).[31]

Lumps of iron pyrite, magnetite, and other materials were mostly shaped into mirrors, pendants, medallions, and headdress ornaments for decorative and ceremonial effect.[32] However, concave iron ore mirrors were apparently used for firing and optical purposes by the Olmec (1500–400 BCE) and Chavin (900–300 BCE) cultures,[33] and ilmenite "beads" may have served as hammers for fine work.[34] The Olmec and Izapa (300 BCE – 100 CE) also seem to have used iron magnetism to align and position monuments.[35] They may have developed a zeroth-order compass using a magnetite bar.[36]

Some Mesoamerican uses of native iron seem to have been military. Steven Jones proposed that the Olmec sewed ilmenite "beads" into protective mail armour or helmets.[34] Iron pyrite mosaics and plates formed protective tezcacuitlapalli (mirrored back flap shields) and breastplate ornaments in the military attire of the Teotihuacan (100 BCE – 600 CE), Toltec (800–1150 CE) and Chichen Itza (800–1200 CE) cultures.[32]

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 relatively abundant, particularly in the Great Lakes region.[3] The latest glacial period had resulted in the scouring of copper bearing rocks. Once the ice retreated, these were readily available for use in a variety of sizes.[3] Copper was shaped via cold hammering into objects from very early dates (Archaic period in the Great Lakes region: 8000–1000 BCE). There is also evidence of actual mining of copper veins (Old Copper Complex), but disagreement exists as to the dates.[3]

Extraction would have been extremely difficult. Hammerstones may have been used to break off pieces small enough to be worked. This labor-intensive process might have been eased by building a fire on top of the deposit, then quickly dousing the hot rock with water, creating small cracks. This process could be 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 ground 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.

Great Lake artifacts found in the Eastern Woodlands of North America seem to indicate there were widespread trading networks by 1000 BCE. Progressively the usage of copper for tools decreases with more jewelry and adornments being found. This is believed to be indicative of social changes to a more hierarchical society.[3] Thousands of copper mining pits have been found along the lake shore of Lake Superior, and on Isle Royale. These pits may have been in use as far back as 8,000 years ago. This copper was mined and then made into objects such as heavy spear points and tools of all kinds. It was also made into mysterious crescent objects that some archaeologists believe were religious or ceremonial items. The crescents were too fragile for utilitarian use, and many have 28 or 29 notches along the inner edge, the approximate number of days in a lunar month.[43]

Hopewell copper falcon, c. 200 BCE – 1 CE, Ohio[44]

The Old Copper Culture mainly flourished in Ontario and Minnesota. However at least 50 Old Copper items, including spear points and ceremonial crescents have been discovered in Manitoba. A few more in Saskatchewan, and at least one, a crescent, has turned up in Alberta, 2,000 kilometres from its homeland in Ontario. It is most likely that these copper items arrived in the plains as trade goods rather than people of the Old Copper Culture moving into these new places. However from one excavated site in eastern Manitoba we can see that at least some people were moving northwest. At a site near Bissett archaeologists have found copper tools, weapons, and waste material of manufacture, along with a large nugget of raw copper. This site however was dated to around 4,000 years ago, a time of cooler climate when the boreal forest's treeline moved much further south. Though if these migrants moved with their metallurgy up the Winnipeg River at this time they may have continued onward, into Lake Winnipeg, and the Saskatchewan River system.[43]

This Old Copper Culture never became particularity advanced, and never discovered the principle of creating alloys. This means that many, though they could make metal objects and weapons, continued to use their flint tools, which could maintain a sharper edge for much longer. The unalloyed copper could simply not compete, and in the later days of the Old Copper Culture the metal was almost exclusively used for ceremonial items.[43]

However this Great Lake model as a unique source of copper and of copper technologies remaining somewhat static for over 6,000 years has recently come into some level of criticism, particularly since other deposits seem to have been available to ancient North Americans, even if much smaller.[45][46]

Plates from Malden, Etowah and Spiro

During the Mississippian period (800–1600 CE, varying locally), elites at major political and religious centers throughout the midwestern and southeastern United States used copper ornamentation as a sign of their status by crafting the sacred material into representations connected with the Chiefly Warrior cult of the Southeastern Ceremonial Complex (S.E.C.C.).[47] This ornamentation includes Mississippian copper plates, repousséd plates of beaten copper now found as far afield as Alabama, Florida, Georgia, Illinois, Mississippi, Oklahoma, and Tennessee. Some of the more famous of the plates are of raptorial birds and avian-themed dancing warriors. These plates, such as the Rogan plates from Etowah, the Spiro plates from the Spiro in Oklahoma, and the Wulfing cache from southeast Missouri, were instrumental in the development of the archaeological concept known as the S.E.C.C.[47]

The only Mississippian culture site where a copper workshop has been located by archaeologists is Cahokia in western Illinois, where a copper workshop dating to the Moorehead Phase (c. 1200 CE) was identified at Mound 34. Gregory Perino identified the site in 1956 and archaeologists subsequently excavated it.[48]

Numerous copper fragments were found at the site; metallographic analysis indicated that Mississippian copper workers worked copper into thin sheet through repeated hammering and annealing, a process that could be successful over open-pit wood fires.[48]

Mace shaped copper headdress ornaments from Moundville

After the collapse of the Mississippian way of life in the 1500s with the advent of European colonization, copper still retained a place in Native American religious life as a special material. Copper was traditionally regarded as sacred by many historic period Eastern tribes. Copper nuggets are included in medicine bundles among Great Lakes tribes. Among 19th century Muscogee Creeks, a group of copper plates carried along the Trail of Tears are regarded as some of the tribe's most sacred items.[49]

Inuit lance made from a narwhal tusk with an iron head made from the Cape York meteorite.

Native ironwork in the Northwest Coast has been found in places like the Ozette Indian Village Archeological Site, where iron chisels and knives were discovered. These artifacts seem to have been crafted around 1613, based on the dendrochronological analysis of associated pieces of wood in the site, and were made out of drift iron from Asian (specifically Japanese) shipwrecks, which were swept by the Kuroshio Current towards the coast of North America.[50]

The tradition of working with Asian drift iron was well-developed in the Northwest before European contact, and was present among several native peoples from the region, including the Chinookan peoples and the Tlingit, who seem to have had their own specific word for the metallic material, which was transcribed by Frederica De Laguna as gayES.[50] The wrecking of Japanese and Chinese vessels in the North Pacific basin was fairly common, and the iron tools and weaponry they carried provided the necessary materials for the development of the local ironwork traditions among the Northwestern Pacific Coast peoples,[51] although there were also other sources of iron, like that from meteorites, which was occasionally worked using stone anvils.[50]