"It gives you a lot more information much more rapidly."
The mica used in the paint likely came from beyond the Maya realm, Goodall said.
"It appears that mica was available in what is now Guatemala. [The Maya] would have had to trade for something like that."
Analysis of such materials used by the Maya offers "an insight into their technology and knowledge exchange and trade networks," she said.
"It gives us an insight into how people in the southern periphery [of the Maya realm] interacted with people in the more northern regions."
The team's findings are published in the Journal of Raman Spectroscopy.
For Special Occasions?
Mica has only been found on the Rosalila temple so far, she said.
"The building was in use for one hundred years—we know that because [the Maya] dated the opening ceremony of the building, and they dated the closing ceremony.
"It was repainted somewhere between 15 and 20 times, but mica was only used, I estimate, in every fourth or fifth repainting. It's not on every layer."
"More than likely there was something very significant about when they used it, if it was only used infrequently," Goodall said.
"The Maya had very regular calendar periods, so the next step is to look at the core [of the paint layers] and see if we can find out the frequency of [mica's] use, which may give us an indication of whether or not it was applied to celebrate one of these period endings, or to mark some significant date."
Cynthia Robin is an anthropologist and Maya expert at Northwestern University in Illinois.
"I think that's a very interesting idea," Robin said of Goodall's theory, "because the Maya numerical system is a base-20 system, so their calendar is based on a 20-year period called a katun.
"We know from hieroglyphs that these katun endings, or these 20-year periods, were important times of ceremony in the life of the king.
"Obviously Rosalila would have been a very important place for Copán's royalty."
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