Copper Production in Mexico

Abstract

Copper is a metal more easily smelted than iron and has qualities of malleability, reasonable tensile strength, and corrosion resistance that made it commonly used in preindustrial times (Forbes, 1950) (Video 1). From the standpoint of the Middle American peoples, it was the most important metal and played a prominent role in the prehispanic metallurgy of Ancient Mexico (Hosler, 1994). Today, copper is one of the cornerstones of the Mexican economy. Most of the Mexican territory lies within a metalliferous zone known as the precious and base metal province ofMexico (Fig. 1). The variety of metals available in this zone is relatively abundant, with copper present largely in the form of ores that have to be extracted from underground deposits. These can be divided into two groups: the easily reducible oxide and carbonate ores, and the more complex ores of the sulfide type. Copper oxides and carbonates are found mainly as cuprite, malachite, and azurite; copper sulfides include chalcopyrite, chalcocite, and bornite. Added to these is native copper, which is found in a pure state and was readily available on the surface in some locales (Ostroumov & Corona-Chavez 2000; Ostroumov, Corona-Chavez, Diaz de Leon, Morales, & Cruz, 2002). In Ancient Mexico, copper was not only the predominant metal but also the most extensively used base material. Between ca. A.D. 650 and 1200 or 1300, indigenous metalworkers from Michoacan, Jalisco, Colima, northwest Guerrero, and the southern parts of the state of Mexico, appear to have worked almost exclusively with native copper and easily smelted oxidized copper ores. But from 1300 to the Spanish conquest in 1521, they combined copper with other elements to produce a variety of alloys, including binary alloys such as copper-silver, copper-gold, copper-arsenic, and copper-tin and ternaries like copper-silver-gold, copper-silver-arsenic, copper-arsenic-antimony, and copper-arsenic-tin (Grinberg, 1996; Hosler, 1988b, 1994, 1995). In the early sixteenth century, the Tarascan kingdom of Michoacan (Fig. 2) was the primary center for metallurgy and metalworking in the region. This technology was largely based on copper and its alloys. Prehispanic copper exploitation reached its height from A.D. 1450 to 1530 in the Tarascan domain. At the time of the Spanish conquest, the Tarascan language used the term tiyamu charapeti haracuquaro to refer specifically to copper miners (tiyamu charapetimeaning copper or “red metal”). Presumably, the use of metal goods such as axe-monies, depilatory tweezers, bells, and other ritual objects and adornments (Fig. 3) among the Tarascans and their neighbors was restricted to the central dynasty and the nobility. Although some utilitarian implements were made, most metal objects were considered to be sacred, to be used for adornment in religious ceremonies, and to enhance the social and political status of the elites (Fig. 4; Hosler, 1988a, 1994; Pollard, 1987, 1993). Artisans from Santa Clara del Cobre, a modern Tarascan municipality in Michoacan, have maintained the traditional techniques for working copper to this day. Essentially the method employed by these contemporary craftsmen is based on the use of the cendrada, a hole in the ground lined with oak ashes which functions as a mold to produce a tejo, a disklike copper ingot, which is then hammered into finished shapes (Videos 2a and 2b). Information provided by written sources, along with the factual presence of smelting waste products (i.e., slag) on the surface of