What I'm assuming is Burlington Chert and not the far more commonly used Mill Creek Chert, this big 7&3/4" by 3&11/16", 1&5/16" Spade is from a Wabash County--Edwards County, Illinois collection off the Wabash River. What you seldom see is both ends having use polish--typically only one end of a spade is heavily use-polished from the sandy river soil. The indented side may have allowed the Spade to be hafted in the center, so it could be flipped over and worked from either end. I would like to have seen how the handle was attached during the Mississippian Era (1250--1400 +/-)--someone working in their corn & squash patch figured out a way do use both ends--and the polish shows it. One face shows a heavy blackening patina with the reverse having a cortex-like roughness you'd expect on Mill Creek Chert (not Burlington). The finder is long deceased, so I'll never be able to ask how the piece was found, creek find, or was it in a charcoal midden? Something colored the white chert, very obviously. Every detail is guaranteed authentic. Shipping is $13, and the piece can be purchased only by check or M.O. as I do not use paypal-type services--Roy A.