science, health & technology
Gold alloys from pre-Columbian Panama: new discoveries
by Eric Jackson
On July 31 at the Smithsonian Tropical Research Institute’s (STRI’s) Tupper Auditorium, long-time STRI archaeologist Richard Cooke and Harriet Beaubien of the Smithsonian’s Museum Conservatory Institute spoke about the state of what we know about pre-Columbian metallurgy in Panama. We know a bit more now because a team led by Beaubien has been studying the metal content of artifacts in the Smithsonian’s collection and that of Panama’s Museo Antropologico Reina Torres de Arauz, with the principal aim of improving the work of those who conserve or restore museum pieces.
Cooke began with an overview of what archaeologists knew about Panama’s pre-Columbian gold. Columbus, he noted, visited Almirante Bay in Bocas del Toro in 1502 and encountered people who went nude except for the golden ornaments they were wearing, and preceded to an expedition in search of gold that went badly in Veraguas.
(Quibian tried to send the Spaniards off to a neighboring tribe’s gold mining spot to get rid of them. The ploy didn’t work and the situation ended in violence between Quibian and his people and the Spaniards and mutiny among Columbus’s crews, making the settlement established at Belen somewhere in Veraguas --- maybe or maybe not the same place that bears the name today --- very ephemeral.)
Then came Balboa and on his heels Pedrarias the Cruel, who occupied the Atlantic side Spanish settlement at Santa Maria La Antigua between 1510 and 1524 and noted that the gold ornaments they found in the natives’ possession was generally alloyed with copper. Pedrarias noted that Cori, the cacique of the ancient community that the former seized to found Panama Viejo, was a gold smelter.
In the course of the Spanish Conquest Parita, one of the great warrior caciques who resisted the invasion died (possibly of battle wounds) and the Spaniards captured the place where his body was being prepared for burial, decked in jewelry, wrapped in cloth and slowly dried by heat. Those burial customs were verified early in the 20th century when archaeologists unearthed Sitio Conte, which dates back to between 700 and 1000 AD.
In 1565 Girulomo Benzoni described the indigenous Panamanian gold working methods, wherein metals were melted over charcoal, with blow pipe bellows, and then worked by hammering.
We know from linguistic that most of Panama’s indigenous peoples are culturally related to the Chibchans of the Colombian highlands, and the stylistic similarities between gold ornaments found in Panama and those from Zenu and Quimbaya in Colombia are striking. We know that Andean cultures were working gold at least as far back as 1000 BC, but the oldest metal objects found in Panama and Central America date back to between 130 and 370 AD. From all that Cooke concluded that what probably happened was the technology moving into the isthmus “from Colombia in a well developed state.”
Beaubien went on to describe how the team she led in Panama was “looking at the materials that have been excavated from a technological perspective. They used non-destructive x-ray fluorescence spectroscopy (XRF) scanning to determine the metal content of 110 pieces in the STRI collection and 382 objects at the Museo Antropologico. (With the latter collection, there were some problems about the provenance of most pieces not being properly documented.) They also looked at the objects under microscopes to see details of hammering marks and crystalline structures that can tell a trained eye how a piece was worked.
Bombarded with XRF, the objects tended to show low-carat mixtures of copper, gold and silver that were “about what you would expect in the ore” that you find at the likely sources of the metals in Panama. That suggests that the people who made pre-Columbian ornaments didn’t mix metals to order but just smelted the mixtures out of the rocks they had and worked the resulting alloys. Adding to that suspicion is that nobody has yet found the remains of implements for mixing alloys.
However, in Sitio Conte and a number of other places there were some anomalous artifacts that varied in the percentage of the various metals in the ore, some with higher silver content more typical of places in Ecuador or Colombia. So were these items imports, or things made by melting imported ores or old imported objects? That’s an unresolved question, further research into which might develop our small but growing body of knowledge about trade networks in the Americas before the Europeans came onto the scene.
It has long been known that most of the gold pendants found in pre-Columbian Panamanian graves were cast by the lost wax method, in which the ornament is shaped in wax, a clay mold is built around the wax model with holes into which molten gold can be poured at the top and the liquified wax might escape at the bottom, and after casting the in this way the gold is further worked by hammering or otherwise.
Clarke noted that he has a broken mold, found by a huaquero in Veraguas, to prove that this method that had been previously inferred had actually been used. Beaubien noted that on some objects bits of the clay mold have been found to further prove this case.
So what’s a museum conservator to do?
Maybe clean the object so the oxidized copper is removed and the gold shines brightly. But maybe not. “Cleaning is a mixed bag,” Beaubien said. It lets you see all sorts of details not apparent on an uncleaned object. However, copper corrosion has biocidal effects that preserves leather, textiles and other organic materials that are in contact with oxidizing copper, and cleaning this patina away will tend to destroy remnants of materials that may be scientifically important in their own right.
Solutions to that dilemma are largely what Beaubien and her team were doing here. The information that they gathered will be useful for all sorts of lines of inquiry, but they’re principally interested in the development of better handling techniques for museums.
Beaubien imparted another bit of metallurgy of vital importance to museums and collectors. “If you have zinc in your object, you have a problem.” That would make it a modern reproduction, not a genuine pre-Columbian artifact.
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