The metallurgical technology that developed in this zone flourished for approximately 900 years. West Mexican metalsmiths incorporated elements introduced from the metallurgies of Central and South America during this long period and elaborated them, inventing totally new ways of handling the material. The timing of these technical events and the historical circumstances surrounding them are difficult to reconstruct. The archaeology of the zone is not as well known as that of other Mesoamerican areas, and analyzed, dated assemblages of metal objects are rare. Nevertheless, I was able to chronologically order major components of the technology by assessing the results of laboratory studies of the RMG collection artifacts (appendix 2) in light of information about those metal objects for which dates are available.

Two technological periods emerged. The first extends from A.D. 600 to A.D. 1200/1300, when metalworkers principally used copper. During this time they fashioned an array of objects by lost-wax casting and by cold work with annealing. The constellation of artifacts makes clear that these artisans were interested in items that visually and aurally expressed their conceptions of the sacred and that reinforced elite status. They disregarded for the most prat metal’s many utilitarian applications. The property of metal that most intrigued them and became most central to their technical experiments was its ability to sound, an interest manifested in myriad bells of different sizes, shapes, and pitches. Smiths also crafted tools from metal during this time, but in far fewer numbers.

By Period 2, which begins between A.D. 1200 and A.D. 1300, metalworkers in this zone became equally intent on developing another property of metal: its color. Their focus on metallic color is dramatically apparently in the range of copper alloys they used (copper-tin, copper-arsenic, copper-arsenic-tine copper-silver) for bells, large ornamental tweezers, and other ritual and sumptuary items. In most cases the alloying element, tin, arsenic, or silver, was present in high enough concentrations to transform the color of the artifact metal to differing hues of gold or silver. They also used bronze alloys (copper-tin and copper-arsenic) for tools, incorporating the alloying element in appropriately lower concentrations. Hot working, a fabrication method required to avoid brittleness when working objects made from copper-tine alloys, was added to the technical repertoire. Most objects made from these alloys were variations on types made from copper during Period 1. However, the superior properties of the allows allowed artisans to explore new design possibilities: they cast larger, more intricate bells; made axes thinner and harder; and crafted wider, thinner, and larger tweezers with symmetrical, tightly wound spirals emerging from each side of each blade. In other words, they used these allows to develop alternatives to existing and familiar objects rather than to devise uses for metal outside of New World cultural experience, such as for metal armor, for example. Period 2 smiths also enlarged the range of ores and extractive and smelting technologies, as they expanded their repertoire of designs and fabrication techniques.