Metallurgy is the extraction and purification of metals, as well as creating metal alloys and fabrication with metal. Indigenous Americans have 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 dated to approximately 5000 BCE.
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 it by alloying it. Indigenous South Americans had full metallurgy with smelting and various metals being purposely alloyed. Metallurgy in Mesoamerica and Western Mexico developed from contacts with South America through Ecuadorian marine traders, it is believed.
To date no one has found evidence that points to the use of melting, smelting and casting in prehistoric eastern North America, a widely accepted observation. Which makes the Mound Builder culture, a lost civilization at the time of Columbus, a fascinating anomaly. They had metal tools as far north as Lake Superior; cf:
Copper. No discovery of the mounds so fills the mind of the Archaeologist with joy as that of copper implements. Copper mining has now by the discovery in the Lake Superior region, of mining shafts long deserted, in which copper was quarried by stone hammers on a large scale, been shown to have been pursued in very ancient times on this continent. It is of intense interest for us to know that not only are there mines found on the south side of Lake Superior, but also at Isle Royale, on the north side just at the opening of Thunder Bay, and immediately contiguous to the Grand Portage, where the canoe route to Rainy River, so late as our own century, started from Lake Superior. According to the American Geologists the traces for a mile are found of an old copper mine on this Island. One of the pits opened showed that the excavation had been made in the solid rock to the depth of nine feet, the walls being perfectly smooth. A vein of native copper eighteen inches thick was discovered at the bottom. Here is found also, unless I am much mistaken, the mining location whence the Takawgamis of Rainy River obtained their copper implements. Two copper implements are in our possession, one found by Mr. E. McColl in the grand mound, and the other by Mr. Alexander Baker in a small mound adjoining this.
Copper Needle or Drill. (See a. Fig. 1.) This was plainly used for some piercing or boring purpose. It is hard, yields with difficulty to the knife, and is considered by some to have been tempered. It may have been for drilling out soft stone implements, or was probably used for piercing as a needle soft fabrics of bark and the like, which were being sewed together.
Copper Cutting Knife. (See e. Fig. 1.) This, has evidently been fastened into a wooden handle. It may have been used for cutting leather, being in the shape of a saddler's knife, or was perhaps more suited for scraping the hides and skins of animals being prepared for use.
Cited in: "Mound Builders" a short article by George Bryce, M.A. LL.D. Professor in Manitoba College and President of the Historical Society, Winnipeg.
Further south, in Spiro Mounds a major Northern Caddoan Mississippian archaeological site located in Eastern Oklahoma, we find refined metal work such as exemplified by Figure 2 - Sheet Metal Copper Ornaments, copper plate, and copper ear plugs.
Fig. 2 - Copper Ornaments from Spiro Mounds, Oklahoma.
Another example of ancient America copper smelting and use is found in the so called Hopewell culture, a Native American culture (or exchange system) thought to have flourished along rivers in the northeastern and midwestern United States from 200 BCE to 500 CE. The Hopewell culture is thought to have obtained copper from the same sources in the Lake Superior region that are thought to have fed the whole Mississippi basin trading system.
Fig. 3 - Hopewell Copper Ornaments
This seemingly reverse evolution - from complex urban settlement, metallurgy, and agricultural production necessary to sustain large urban civilization to the simple hut and village stone age settlement characteristic of the Americas north of the Rio Grande at the time of Columbus - has fermented no shortage of speculation of a "lost culture".
It seems as if this "lost culture" was swept away; their mines deserted and filled up with debris; their arts of agriculture, metal working and pottery making, lost; and only the mounds and their contents are left.