Maya blue is the man-made pigment that colored the Mayan world, associated with sacrifice and Maya deities such as the rain god Chaak.
Impervious to the effects of chemical or physical weathering, Maya blue was applied to pottery, sculpture and murals of Mesoamerica largely during the Classic and Postclassic periods (AD 250-1520), playing a central role in ancient Maya religious practice. It was also coated the victims of human sacrifice and the altars on which they were killed.
According to Past Horizons:
Scientists have already discovered that it is produced by chemically binding indigo to the clay mineral palygorskite by carefully controlled heating, though it is still not absolutely clear exactly how the Maya actually made it.
However, science and anthropology teamed up to solve another question concerning the brilliantly hued pigment and the researchers have established a link between contemporary indigenous knowledge and the ancient sources of the mineral.
Research on sources for palygorskite has been ongoing since the late 1960s. It was recently discovered that palygorskite was well known among indigenous potters of Ticul, Yucatán. These contemporary Maya use palygorskite as a key component of their own pottery production as a temper and also prescribe the mineral for medicinal purposes for intestinal problems.