Excavations at the Copper Smelting Site of El Manchon, Guerrero, México

Final Report

The work described here and funded by FAMSI, addresses one of the most significant gaps in our understanding of the copper-based metallurgy that developed in ancient Mesoamerica. Until our excavations of El Manchon, we had scant archaeological evidence of metal production–smelting, and processing, and where those activities were located–although we do possess ample documentation of fabrication methods, alloys used, (copper-tin, copper-arsenic bronze, and copper-silver alloys) the relationships with South America, and the overall sumptuary emphasis of this technology. El Manchon is one of several copper smelting sites I located in the Balsas drainage of Guerrero in a 1997 survey. El Manchon is thus far the only such smelting site reported in Mesoamerica. The site is situated at 1400 meters above sea level in the Sierra Madre del Sur of Guerrero and consists of two physically distinct habitation areas characterized by long, low rectangular mounds measuring from 12 to 22 m in length, 2.5 m in width, and about 2 m in height. There also is a large smelting area between these two areas delimited by two seasonal streams. The smelting area is covered with a glassy-like slag and disturbed furnace remains. The site itself stretches across approximately 1 km, is crosscut by deep barrancas and arroyos, and is highly eroded.

With the support of FAMSI, we completed one field season at the site which is discussed in the Interim Report. We also constructed a rudimentary base camp. The investigations of the smelting area consisted of complete excavation and mapping of one of the furnaces. We recovered volumes of slag and numerous samples of copper ore, and a number of potsherds. This particular furnace had been badly disturbed by tree roots, making the original configuration nearly impossible to determine. We also tested several of the mounds in the storage/habitation areas and opened two of them horizontally. We were able to recover caches of potsherds (that look like a midden) and to collect a number of obsidian and quartz samples from within these mounds, but found no structured evidence of domestic or craft activities (cooking or other). We likewise were unable to identify postholes that might have supported a wooden or thatch superstructure. We so far are unable to definitively identify the function or use of these long rectangular structures, but plan to explore this problem further in the next field season.

Click on images to enlarge.

During June of 2002 and June of 2003, we undertook preliminary analysis of the pottery as well as the copper ores and slags that we recovered from the furnace. We were able to identify plates, jars, shallow bowls, a cup with a pedestal base, and numerous fragments of either incense burners or large ladles. All of these are highly eroded, but many consist of red decorative elements on a white slip. The red paint has been applied before firing. Our studies show that the copper ore is malachite and cuprite, associated with iron oxide in a quartz matrix. Experimental work shows that the ore is self fluxing, which lowers the melting point of the copper. Our work on this aspect of the smelting technology continues. We plan to source the obsidian (which includes green, grey, and black) and to submit a number of carbon samples for analysis (we collected approximately 100 samples). The results of these and other on-going laboratory studies, in conjunction with further excavations, will amplify our interpretation of this smelting technology and this site.

Click on images to enlarge.

Comments

This research project will constitute a long-term undertaking, in part because we are working in an area that is virtually unknown archaeologically. The location of El Manchon, as well as the material remains (pottery, architecture) suggests that this was not a metal production site dominated by any of the well-documented contemporary social groups (Tarascan, Matlatzinca, Mexica). We do have two preliminary dates that cluster around 1300 A.D., but these should be considered very approximate. We do not yet know the ethnic affiliations of the people living in this mountainous area of Guerrero. These data will begin to emerge as we continue the analysis of the pottery, in further excavations and in comparative studies. We also do not know where the copper ingots were processed following smelting. We may yet recover them at the site of El Manchon itself, or alternatively, several sites lie within close proximity of El Manchon, and at least one of these is characterized by monumental architecture. Local people report that they have recovered copper rings from that site and this area may be appropriate to explore in future work.

Previous Page  |  Table of Contents  |  Next Page