Mississippian culture pottery is the ceramic tradition of the Mississippian culture (800 to 1600 CE) found as artifacts in archaeological sites in the American Midwest and Southeast. It is often characterized by the adoption and use of riverine (or more rarely marine) shell-tempering agents in the clay paste. Shell tempering is one of the hallmarks of Mississippian cultural practices. Analysis of local differences in materials, techniques, forms, and designs is a primary means for archaeologists to learn about the lifeways, religious practices, trade, and interaction among Mississippian peoples. The value of this pottery on the illegal antiquities market has led to extensive looting of sites.