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Researchers from Mexico’s National Institute of Anthropology and History (INAH) and the National Autonomous University of Mexico (UNAM) confirmed cinnabar and hematite were used to elaborate the murals in Teotihuacan between 200 and 300 A.D.
Researchers studied the most representative murals of the Quetzalpapálotl Complex, located southwest from the Moon Square, that holds structures from early and late phases.
The paintings are located at the Quetzalpapálotl Palace, the Jaguars Patio, the Temple of Feathered Snails, and the South Complex.
UNAM and INAH experts identified, for the first time, that cinnabar and hematite were used to create reddish hues in the city's early decorations.
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The discovery is meaningful because, so far, experts had only identified loose fragments that date from the last style and technological development stages of the pre-Hispanic city, between 350 and 550 A.D.
In addition to the presence of cinnabar and hematite in the Teotihuacan murals, the experts also detected the use of plastering at the stuccos, a material that had not been seen before.
In order to identify the cinnabar and the hematite, the experts performed portable X-ray fluorescence spectrometry (pXRF) tests. This instrument allowed the experts to carry out a fast in situ analysis without the need of extracting a sample from the wall.
In order to validate the results of the pXRG tests, they used scanning electron microscopy (SEM) equipped with an Energy Dispersive X-Ray Spectroscopy (SEM-EDS) and Raman spectroscopy to examine the small samples extracted from the three architectural complexes .
The selection of the spaces was done “because they contain medium and light reddish hues in their pictorial composition. Just a few of them included red-orange hues, such as the door frame of the Substructure of the Feathered Snail and a monochromatic wall of the South Complex,” as reported by the experts in a study published on the Journal of Archaeological Science: Reports.
Cinnabar was detected at the Temple of the Feathered Snails in the representations of four-petal flowers and the body of seashells, as well as under blue pigments of the quetzal feathers depicted at the Palace of Quetzalpapálotl, in the central patio. The rest of the cases showed the application of iron oxides, like hematite, in different hues.
Cinnabar was scarce in that region, so it might have possibly been imported from the Central Plateau elsewhere (perhaps from Querétaro’s Sierra Gorda or from Guerrero or Michoacán), which made it one of the most expensive and symbolical pigments of the pre-Hispanic palette, which explains why its use was limited to specific decorative elements and was related to superior social hierarchies, such as the ones that inhabited the Quetzalpapálotl Complex.
“This mineral was also a symbol of wealth, power, and magic properties related to the gods of the underworld. The high esteem for cinnabar does not only lie in its rareness but also in the pigment’s chemical characteristics since the color’s behavior is similar to blood, which grants it a special connection.”
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As part of the in situ works, the Mexican researchers identified the use of plastering in the production of stucco which had not been previously reported in Teotihuacan .
Additional analysis with SEM-EDS and Raman spectroscopic tools confirmed the use of plastering.
Since the material is less resistant, it is probable that this calcium sulfate was used in murals with paintings and decorations that were finer and less exposed to the environment; nevertheless, the use of plastering “tells us about a change in the technology to produce stucco, a matter that must be further studied by future research.”
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