This small native American Pelting hammer would've been used on small game furs for helping to soften the pelt to be used in a variety of ways.  The green stone is Serpentine and has a sharp edge of one side that can be seen in the pictures.  It's very hard to tell the age of this piece although our sense of it is that it has been around awhile. The hand carved wooden handle is some kind of a hardwood perhaps Ash or Elm.