This artifact is called a celt. A celt is an ungrooved axe head made and used by the original inhabitants of what is now the Midwestern United States. I did not find this piece but it has been in my family for more than 50 years. The celt was probably found by my Grandfather or perhaps one of my uncles on a farm west of town where my Dad and his brothers spent time during the summer.
In the book "Ohio's Indian Past" by Lar Hothem I was suprised to find a photograph of a very similar hardstone celt that was found in North Central Ohio. The description accompanying the photograph in Lar's book dates the Hopewell squared-poll type celt to the middle woodland period roughly 2000 years ago. According to the book the celt was used for a multitude of chopping and pounding chores. For example it is believed that stone axes and celts were not used to fell trees but instead to shave off the bark at the base of the tree trunk which would quickly kill the tree. This was done to create a sunny and shade free glade in which to plant crops. During the woodland period, 1000 BC - AD 800, the transition from a hunter-gatherer to an agricultural based existience was probably well underway. When I hold this primitive tool in my hands and feel it's heft I can imagine how useful it would have been for digging and chopping. It is just my opinion but I believe that a celt like mine could have been used as a hand held implement and not fixed to a wood or bone handle.