What material is the Aztec Sun Stone primarily made of?

The Aztec Sun Stone is primarily made of basalt.

The enormous Mexica stone was carved from olivine basalt, a dark volcanic rock. Geologist Ezequiel Ordóñez identified its parent rock as material from the Xitle volcano, probably quarried near San Ángel or Xochimilco and transported roughly 22 kilometers to Tenochtitlan.

The monolith is about 3.6 meters across and 98 centimeters thick. Although commonly called the “Aztec Calendar Stone,” that label can mislead: scholars debate its precise function, and many believe it served as a ceremonial basin or ritual altar rather than simply an astronomical calendar.

It was probably carved during the reign of Moctezuma II, between 1502 and 1520. After the Spanish conquest it was buried, then rediscovered on December 17, 1790, during construction work in Mexico City. Its dark stone material is not granite, jade, or obsidian; those are other rocks associated with Mesoamerican art and tools.