Yes Grinder is what they call them here. Some of the old timers call them pounders but Grinder or Pestle would be a better term for their use. Where did you pick it up from?
I found this one along the Ohio River in Aberdeen Ohio. Thanks to everyone for the info. I've found a lot of stuff but wasn't really sure what it was used for. The stone ring I posted has about drove me crazy trying to figure out what it was and who made it.