When the international press covered the news that researchers at Teotihuacan had encountered liquid mercury in their excavations of a tunnel associated with the Temple of the Feathered Serpent, I was called by a reporter interested in knowing whether similar finds existed elsewhere in Mesoamerica.
Luckily, I knew the answer: ancient Honduras (and adjacent Guatemala) were central locations for Mesoamerican use of liquid mercury. Here’s why.
Cinnabar, the red powdery mineral mercuric sulphide, was in use in Central America by the time when people in Formative Honduran sites like Puerto Escondido, Copan, Los Naranjos, and the Cuyamel Caves created pottery with deeply carved designs rubbed with red pigments. While red pigments on early pottery from Honduras have never (to my knowledge) been tested chemically, cinnabar has been reported from sites in Mexico, including La Venta, Chalcatzingo, and Izapa, and museums often describe the red pigment on ceramics similar to those from Honduras as cinnabar.
A long time later, liquid mercury appears in archaeological sites dating to the Classic Period (between 400 and 800 AD). The majority of reported finds are from the highlands of eastern Guatemala and western Honduras, at Lake Amatitlan, Kaminaljuyu, and Quirigua in Guatemala, and Copan and El Paraiso in western Honduras.
A major point of disagreement among archaeologists writing about finds of liquid mercury has been whether it was collected from naturally occurring deposits, or produced by processing cinnabar, burning it in closed vessels.
David Pendergast, excavator of a ballcourt cache at Lamanai, Belize described the liquid mercury there as likely collected in the highlands of Honduras or Guatemala as native drops of liquid mercury in cinnabar deposits.
USGS reports from the 1950s do describe some liquid mercury in Honduran cinnabar deposits near Tegucigalpa. Some of these deposits were exploited by Spanish colonial miners who used mercury in processing silver ore.
However, these geological resources are far from the zone where archaeological finds of liquid mercury are reported, and no archaeological sites in this area have produced evidence of contact with places like Copan or Quirigua, let alone sites in Belize.
Other cinnabar deposits are present in the Department of Santa Barbara, much closer to the archaeological locations where liquid mercury has been found. There are no reported incidences of native mercury in these deposits. But liquid mercury can be produced by burning cinnabar under certain conditions.
At Copan and Quirigua, there is evidence that this was how liquid mercury found there was actually produced.
A cache associated with carved stone Monument 21 at Quirigua contained a deposit burned in place. The excavator, Professor Wendy Ashmore of UC Riverside, argued that the burning of cinnabar in this cache produced the liquid mercury found there.
At Copan, a deposit in the Margarita tomb similarly includes signs of burning, with both unconverted cinnabar and liquid mercury present. Harriet Beaubien of the Smithsonian Institution commented that she
was involved in the excavation of a cache associated with the Margarita South Offering Platform at Copan in 1993, which produced a large quantity of liquid mercury. The stone “box” had, among other items, a large lidded ceramic bowl containing the remains of a turkey. Everything was very very heavily burned (blackened), and I believe that quantities of cinnabar were included in the deposit, transformed to liquid mercury in a reduction environment. Yellowish stains (not tested) suggest sulfur-rich products, the leftover component of cinnabar’s decomposition.
So, did the people of the ancient southeastern Maya area invent this process, and innovate the use of liquid mercury?
Dating of the Teotihuacan cache suggests not.
The deposits being explored by the current Teotihuacan project under the Temple of the Feathered Serpent predate 400 AD. Sergio Gomez, the lead archaeologist on the team slowly excavating the contents of the ancient tunnel below the pyramid, has suggested that the tunnel might have been sealed off as early as 200-250 AD.
That would make the presence of liquid mercury substantially earlier at Teotihuacan than in the caches from Copan, Quirigua, and other nearby sites. Only the cache from Caracol has similarly early dates.
With the new discovery at Teotihuacan, we can now say with certainty that mercury was used in ritual before 400 AD in Mexico. The technology required to produce mercury from cinnabar was entirely within the reach of people in this area as soon as they were able to fire pottery (long before 1000 BC).
In Honduras and bordering Guatemala, the practice of burning offerings was an important part of ritual. The red pigment cinnabar, locally available, may have originally been burned as a ritual gesture– producing a model of transformation in color and texture from red powder to silvery liquid.
It may be no accident that this practice became important at the same time, and in the same area, where other burial practices, cache and burial contents, and imagery suggest that Teotihuacan was an important point of reference in political and religious life.