We used to find quite a few artifacts when we didn't have cabs on tractors, high speed equipment reduced what we find now.

The round stones mentioned in the quote above sounds to me like net weights.  According to what I have heard, the Indians chose well rounded stones to weave into nets used to throw over game, usually used by younger braves not yet skilled with an arrow.

Interesting someone mentioned granite in this thread, BIL found a hatchet head that had a lot of green on it, someone took it to a professor at the University of Illinois who said the stone it was made from was only located around Michigan or Wisconsin.  He said it proved there was a lot of trading going on between tribes a long distance away.  He also said the green was caused because of it being placed on the chest of the Brave when buried, so he could use it in the great hunting ground.  No bones were found near the artifact, BIL just found it in his garden.