Mexican murals store magnetic data

Tiny magnetic particles found in the pigments of some ancient Mexican murals record the direction of Earth’s magnetic field when the paint dried, a phenomenon that could help archaeologists determine the age of frescoes throughout Mexico and Central America.

The red pigments in murals painted by the artists of pre-Columbian civilizations in the New World often contain bits of magnetite, an iron oxide mineral, says Avto Goguitchaichvili of the National Autonomous University of Mexico in Mexico City.