Here are some pictures of some mysterious rocks that I found while looking for fossils in Loveland, Ohio (a small town just outside of Cincinnati). There are actually a LOT of fossils here because this was the site of a shallow sea in the Ordovician period, about 500 million years ago. So, there are great shells and corals and reportedly there are trilobites - but, I have not found any yet. I was questing for trilobites when I found THESE instead. Take a look:
Sorry, I have trouble with hot links -- so, far they are all cold. Anyway, PLEASE look at the article, because at the end there are pictures that are strikingly similar to mine. One of the pictures in the article is of a rock with a hole in it that they would have used to put a stick or something into and start a fire. I found one almost just like it! The pictures are below. There is a hole on the top and one on the bottom that almost lines up with it - the hole does not go all the way through.
The important thing I learned from the article is that the people would find a tool that naturally approximated what they needed, and then they would just have to "work" it a little bit to devise a tool. The article says that archaeologists often overlook these crude stone tools because many of their features are naturally occurring with only a few "worked" elements.