Metallurgical Characteristics of North American Prehistoric Copper Work

The use of native copper in some prehistoric cultures of North America was both extensive and technically skillful. The remains of pits sunk into every major native copper lode in the Lake Superior region (Griffin 1961; Drier and DuTemple 1961: 16; Quimby 1960: 52-63; West 1929) show that the material was mined in quantity. Float copper, found on the surface, was also used. The Indians appreciated some of the properties of copper and made use of these in shaping tools, weapons, and ornaments of high-quality workmanship. Figure 1 shows typical examples of the thousands of beautifully shaped native copper artifacts which have been found in mid-North America. The development of metallurgical techniques is usually supposed to follow a progression of hammering, annealing, melting the native metal, smelting ores, casting, and alloying. Curiously enough, the techniques of copper working in North America evolve only through the hammering and annealing stages, and apparently they remained at this level for centuries. In this paper the authors examine some of the metallurgical properties of the artifacts and the native copper from which they were made.