Well now, from time to time folks put stone pieces on this site and ask if it is a geofact or an artifact. Over the years on various sites I have found a number of geofacts that had been picked up and used by early American Indians. After some modification and use the former geofact becomes an artifact.
One of the better examples in the first photo is the naturally formed chert platform for grinding red ocher. This piece is Cummins Creek Chert and the only way for it to get to this hillside campsite was for someone to bring it up here. The full-groove in the hammer stone or pestle is also naturally formed. Someone in the distant past found it on a gravel bar, realized the possibilities, picked it and brought it home. The big quartzite hammer-grind stone is worn completely flat on one side. The stone with the finger groove is naturally formed but the bottom is worn smooth from use.
In the second photo the round hole in the hand stone is naturally formed . The top of the stone is worn smooth and was found in the same strata with the
drillbit illustrated here with a bow, brace and drill. The long chisel occurred naturally and was modified by someone who sharpening the tip.
The third photo is of some points that came up in the sifter this morning. I included the broken blade because of the rare craftmanship and the needle tip.
One of the things to look for with geofact-artifacts is something that is out of place, such as a riverine quartzite piece on top of a hill. If it catches your eye, pick it up and examine it for dings or other evidence of use. It may prove to be a treasure.