A lot of the pieces I see are stamped with corn cob. Others look like pine straw, where they wrapped the pot during firing. If you break a piece and look at the middle it will have little white specks. That is muscle shell they put in it for tempering. There is a site close to me where you can't walk without stepping on it. It is only about 250 to 1500 years old from the mississippian period. Cool finds!!!!
Luck is where preparation and opportunity meet