Visitors to many of the archaeological sites in Mexico, Guatemala, Belize and Honduras are often struck by the bright blue paint on architectural sculptures and frescoed murals at these sites. This remarkable hue, with its brilliant and distinctive character, also adorns pottery and figurines in exhibitions of Maya art and archaeology (Figure 1).

But for the ancient Maya, this Maya Blue was more than just an attractive blue pigment. Its use and meaning were sacred, symbolizing water and rain among other meanings, and was associated with the rain god, Chaahk. Its use began in the Terminal Preclassic period, approximately 50 BC to AD 200, but became widespread in the Late Classic period on architecture, figurines, murals, and elite ceramics. This continued throughout Mesoamerica before the sixteenth-century Spanish Conquest, and on into the Colonial period on codices and murals in monasteries and convents.

But Maya Blue was not just a sacred and beautiful pigment; it is one of the great technological achievements of the ancient Maya as one of the world’s most unusual pigments. Most pigments are either organic, derived from plants or animals, or inorganic, based on blue or green minerals. Maya Blue, however, is a hybrid of an organic component, indigo—or its precursors—and an inorganic component, the unusual clay mineral palygorskite. Because it resists fading and attack by strong solvents such as acids, chemists have devoted many hundreds—if not thousands—of pages to understanding how and why the pigment differs so much from one of its constituents, indigo.

 At some point late in the Terminal Preclassic (ca. 50 BC-AD 200), the Maya discovered that heating a mixture of a small amount of the extract of the indigo plant with a mineral that the Maya today call “white earth” (sak lu’um) produced the beautiful, fade-resistant blue pigment now known as “Maya Blue” (Figure2).

While indigo comes from the widespread Indigofera suffruticosa plant, palygorskite— which continues to be used by the present-day Maya for medicinal purposes and pottery tempering—comes from only two known sources in Yucatán: a location northeast of the town of Ticul, and a mine in a sinkhole (cenote) in the village of Sacalum (Figure 3).

In 1967, Dean E. Arnold, the lead author of the present study, proposed that the mine in the cenote of Sacalum was the source of the palygorskite used in Maya Blue. Subsequent research by multiple scientific teams has demonstrated that the trace element compositions of the palygorskite deposits in Sacalum and near Ticul differ from one another and from those of other palygorskite deposits in Yucatán. Later, researchers determined that the trace element composition of palygorskite from these two sources matched samples of Maya Blue from Chichén Itzá and Palenque.

Did the palygorskite in Maya Blue from other sites also come from these two contemporary sources? To find out, the authors submitted twenty samples of Maya Blue on pottery from the early Late through the Terminal Classic periods (AD 680-900) recovered from the modest center of Buenavista del Cayo (ancient Komkom) in central western Belize for trace element analysis by laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS). The ceramics were collected by Joseph W. Ball and Jennifer Taschek, both of San Diego State University, during their excavations at Buenavista between 1984 and 1989. The analyses were carried out by Dr. Laure Dussubieux in the Field Museum’s Elemental Analysis Facility. Three of the samples proved too small for instrumental analysis, but the results from the other seventeen indicated that the palygorskite in these samples most likely came from Sacalum, 375 km northwest of Buenavista.

But how did the palygorskite—and the knowledge of how to make the sacred blue pigment—come to be transported to such a distant location? Because the pigment held significant cultural and ceremonial importance, it was more likely to have been conveyed through high-status sociopolitical or ceremonial exchanges than through ordinary commercial trade. The authors believe that the routes for this diffusion involved maritime routes along the north and east coasts of the peninsula and then up the Belize River to Buenavista, which sits at the navigable upriver extreme of this waterway. It also served as the gateway to the interior lowlands of the Eastern and Central Petén.

Maya Blue initially appeared at Buenavista as a rare architectural embellishment in the sixth century, and on rare, imported ceramics in the late seventh century. Thereafter, its use gradually increased over the eighth century on locally produced and painted Belize Valley wares, peaking in the early ninth century before disappearing around AD 860.

Our research revealed that Maya Blue pigment, so important in the Late and Terminal Classic ceramic and architectonic traditions of the Belize Valley and the Eastern Petén, was the product of extracts of the locally available indigo plant, the clay mineral palygorskite from Sacalum in faraway Yucatan, and the esoteric knowledge needed to combine these two components into the beautiful, color-fast hue. More importantly, this research has demonstrated the potential of using LA-ICP-MS of Maya Blue as another effective methodology for investigating long-distance social interactions throughout Mesoamerica.

The article “Palygorskite from Sacalum, Yucatán in Maya Blue From the Eastern Maya Lowlands: New Evidence From Buenavista Del Cayo, Belize and La-ICP-MS Analysis” is out now, open access, in the journal Ancient Mesoamerica.