Petrographic evidence shows that pottery exchange between the Olmec and their neighbors was two-way.

Petrographic thin sections of pottery from five Formative Mexican archaeological sites show that exchanges of vessels between highland and lowland chiefly centers were reciprocal, or two-way. These analyses contradict recent claims that the Gulf Coast was the sole source of pottery carved with iconographic motifs. Those claims were based on neutron activation, which, by relying on chemical elements rather than actual minerals, has important limitations in its ability to identify nonlocal pottery from within large data sets. Petrography shows that the ceramics in question (and hence their carved motifs) have multiple origins and were widely traded.