Mysteries of "Sacrificial" Maya Blue Pigment Solved?

Ker Than
for National Geographic News
February 26, 2008
An ancient clay bowl from Mexico is providing new clues to the production and role of a hardy blue pigment widely employed by the ancient Maya.

The find also helps explain a mysteriously thick layer of blue silt that archaeologists reported at the bottom of a sacrificial sinkhole where the bowl was recovered more than a century ago.

The pigment, known commonly as Maya blue, was used to paint offerings, pottery, murals, and even the bodies of humans before ritual sacrifices. (Related: "Ancient Maya Used 'Glitter' Paint to Make Temple Gleam [February 7, 2008].)

Scientists have long known the basic chemical components of the pigment, which has a remarkable ability to resist age, acid, weathering, and even modern chemical solvents.

"Unlike a lot of natural pigments that may fade, [Maya blue] is very stable," said Gary Feinman, curator of Mesoamerican anthropology at the Field Museum in Chicago, Illinois.

But the exact recipe, along with the tools the Maya used to create the pigment and the circumstances surrounding its use, were unknown.

The new research by Feinman and colleagues, which appears online today in the journal Antiquity, may answer some of these questions.

Sacrificial Sinkhole

Lead study author Dean Arnold of Wheaton College in Illinois first came across the pottery bowl while searching through the Maya collection at the Field Museum.

He noticed that the bowl contained a wedge of preserved incense dotted with white flecks and a blue pigment.

The bowl had been discovered more than a century ago at the bottom of the Sacred Cenote, a large sacrificial sinkhole at the Maya site of Chichén Itzá, which was associated with the rain god Chaak.

More than a hundred humans were sacrificed to the deity at this site. (See an interactive map of key Maya sites.)

Analyses revealed the incense was made of a copal, a tree sap whose smoke the Maya believed nourished the gods.

The pigment was the famed Maya blue, and the flecks were bits of a white clay mineral called palygorskite.

According to previous studies, Maya blue is made by fusing palygorskite with pigments from the leaves of the indigo plant.

But the two ingredients do not readily combine, and it was unknown how the Maya fused them.

Archaeologists had suspected that copal was important to the production of Maya blue, and the new findings seem to confirm that theory.

"Our study suggests that heat and copal incense likely were key elements used to fuse the two components together," Feinman said.

Symbolic Value

Taken together, the bowl's history and its contents support the idea that Maya blue had great symbolic significance, study leader Arnold said.

Indigo, palygorskite, and copal—all associated with healing—were used individually as medicines by the ancient Maya.

"The offering of three healing elements thus fed Chaak and symbolically brought him into the ritual in the form a bright blue color that hopefully would bring rainfall and allow the corn to grow again," Arnold said.

The pigment's importance to the Maya is perhaps best illustrated by a 14-foot (4-meter) layer of blue silt that was discovered at the bottom of the Sacred Cenote when it was first excavated in 1904, the researchers say.

At the time archaeologists did not know what the blue material was, but the new findings strongly suggest it was Maya blue precipitate that had washed off of pottery and human bodies cast into the sinkhole.

Mary Miller, an art historian at Yale University in Connecticut who was not involved in the study, called the new findings "an exciting addition to the corpus of what is known about this stunning and tenacious pigment."

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