The Cascajal Block is a tablet-sized writing slab in Mexico, made of serpentinite, which has been dated to the early first millennium BCE, incised with hitherto unknown characters that may represent the earliest writing system in the New World. Archaeologist Stephen D. Houston of Brown University said that this discovery helps to "link the Olmec civilization to literacy, document an unsuspected writing system, and reveal a new complexity to [the Olmec] civilization."