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Banner image: Detail听from a document called the Grolier Codex. (Credit: Gerardo Guti茅rrez)

Josue Sa茅nz Trevi帽o, a renowned collector of antiquities, probably didn鈥檛 know what he was getting himself into when he unwrapped the little manuscript, no bigger than a cocktail napkin.

The year was 1965. Sa茅nz, then president of Mexico鈥檚 Olympic Committee, had just hopped on a plane and flown to a spot somewhere near the states of Chiapas or Tabasco. There, as Sa茅nz would later reveal, he met with a group of grave robbers who presented him with the booklet.

鈥淎ll of this was shady but, sadly, not illegal at the time,鈥� said Gerardo Guti茅rrez, a CU Boulder archaeologist who studies pre-colonial peoples of the Americas.听

It was also potentially the find of Sa茅nz鈥檚 life. The document itself bore a series of paintings on bark paper depicting the passage of Venus through the night sky. They were intricate, colorful and, at least on the surface, seemed to date back hundreds of years to the height of Maya civilization. 听

As far as scholars knew, only three such books, called Maya codices, had ever been discovered, and all of them were sitting in museums in Europe. What Sa茅nz held in his hands might be a long-lost fourth.

It could also have been a forgery.听

More than four听decades after that fateful plane ride, Guti茅rrez served on a scientific team that set out to answer the question once and for all. The archaeologist turned art detective uses high-tech tools to probe the secret lives of paintings, ceremonial masks and more.听

Recently, for the Pre-Colombian Society of Washington, D.C. The archaeologist, whose career spans two decades and several continents, is using the opportunity to reflect on his most nerve-wracking case to date鈥攐ne that brought him face-to-face with what may have been the oldest surviving book from the Americas.

鈥淚 was worried because I was walking into a debate that had gone on for decades, and nobody was going to be happy about the results,鈥� said Guti茅rrez, an associate professor in the Department of Anthropology. 鈥淚t was very risky.鈥�

The detective in his lab

A couple of years later, Guti茅rrez shows off what he calls his 鈥渕obile laboratory鈥� from his office on campus. It includes a wide range of portable instruments, such as ultraviolet and infrared lights and several different kinds of microscopes.听

He pulls out one scientific tool, a device called an X-ray fluorescence (XRF) spectrometer, that looks like a sci-fi ray gun.

鈥淒o you remember in Star Trek when they would have to identify the components of objects on different planets?鈥� he said. 鈥淭his does the same thing.鈥澨�

It also helps Guti茅rrez to pursue his obsession with color and, in particular, pigments.听

The archaeologist has brought his mobile lab with him to collections from all over the world in American and Mexican museums through an effort he calls the Colors of History Project. Guti茅rrez uses these tools to examine the chemistry underlying everything from ancient cave paintings to Renaissance-era portraits.听

His favorite pigment is called Maya Blue. Made by mixing the indigo plant with a type of clay, this molecule looks more turquoise than a deep blue. The color appears in a lot of artwork from buildings in pre-colonial Mesoamerica to Spanish colonial churches, in part because of its staying power.

鈥淚t鈥檚 really an immortal pigment,鈥� Guti茅rrez said. 鈥淵ou can put anything on it鈥攕trong acids and bases. You can expose it to weathering and, more importantly, time. It won鈥檛 degrade. The only thing Maya Blue can鈥檛 resist is direct fire.鈥�

It was Guti茅rrez鈥檚 experience with this immortal pigment that brought him face-to-face with the manuscript that Sa茅nz purchased all those decades ago.

The case of the codex

What happened in the years after Sa茅nz bought the booklet off of the grave robbers in 1965 is murky. In 1972, however, it turned up in New York where its pages were displayed on black velvet in the Grolier Club, a haunt for the city鈥檚 blue bloods.听

Known as the Grolier Codex, the book soon became caught up in the rivalry between two competing schools of Maya scholars. One claimed that the book was authentic, while the other contended that the manuscript was merely a clever forgery.

The debate lingered for decades. In 2016, a U.S.-based team claimed that it solved the mystery, but some experts considered the researchers too biased and downplayed their results.

One year later, Mexico鈥檚 National Institute of Anthropology and History decided to put the question to rest for good. It assembled a dream team of scientists from several different universities in Mexico鈥攑lus Guti茅rrez and his CU mobile lab.听

The researcher still remembers seeing the book for the first time. By that point, it was stored in the basement of the National Museum of Anthropology in Mexico City in a vault Guti茅rrez compares to Fort Knox. He was blown away by the sheer detail of the paintings. One illustration depicted a being who scholars call the Death God wearing a jaguar headdress. Another showed a second god with the legs of an eagle.听

鈥淚t was just amazing seeing it,鈥� he said. 鈥淏ut as a scientist, I had to hold my feelings in.鈥�

Guti茅rrez and his colleagues probed the document using his XRF machine, microscopes and more. But the silver bullet came down to Maya Blue. Using X-ray fluorescence spectrometry and other tools, the team found the pigment hiding in an illustration of water.听

That was significant, Guti茅rrez said, because at the time when Sa茅nz met with his grave robbers, not a single person knew how to recreate the pigment.听

鈥淚 knew we had it,鈥� Guti茅rrez said. 鈥淏ut it wasn鈥檛 until one of the other teams sent me a photograph by email of a scanning electron microscope image that clearly showed Maya Blue when I said, 鈥榊es, that鈥檚 it.鈥欌��

The book, in other words, was undeniably a fourth Maya codex. Other analyses suggested that the manuscript dated back to the 11th or 12th centuries, a timeline that made it the oldest known American book. It also remains the only codex that resides in Mexico.听

With the mystery solved, Guti茅rrez is planning his next high-profile case. He鈥檚 examining whether there might be two different recipes for making Maya Blue鈥攐ne pioneered by Maya around 300 AD, and another by the Mixtecs and Aztecs much later in 1300 AD.听

For now, Guti茅rrez is satisfied that the fourth Maya codex, still in its vault, will finally get some peace.听

鈥淚t鈥檚 time to stop using it as a lab rat where every year another team comes and takes pieces of it,鈥� he said. 鈥淲e have to begin to treat this document with the respect it deserves.鈥�