I'm not sure if this is an artifact or not. The circular shape on the side doesn't seem like it would be natural, but what could this be? The stone fits nicely in my hand and is smooth to the touch.
Welcome! If it's near an old homestead it could have been used as a bed warmer. Smooth river stones were warmed on stoves then wrapped in heavy cloth and placed in the bed to warm your feet. Way before water bottles and electric blankets!