Tough and tiny zircon crystals have helped researchers rule out an enormous volcanic blast as the source of ash used to make Maya pottery, deepening this long-running archaeological mystery.

"While we're a little sad not to have solved the mystery, we're really confident we can say the most likely source quite conclusively isn't a match," said lead author Kevin Coffey, a geology master's student at the University of California, Los Angeles.

However, the results did a reveal a tantalizing new pottery puzzle for scientists to solve — whether the Maya's ash came from one volcano or many spewing cones. [Image Gallery: Stunning Mayan Murals]

"Every time I turn another leaf in this thing, it opens up a new problem," said study co-author Anabel Ford, director of the MesoAmerican Research Center at the University of California, Santa Barbara.