If you can... take it to the U of I anthropology dept and have a prof. inspect. If it's an Indian tool, they'll know who made, when it was made, and what it was used for.
I have a perfectly round stone, about the size of a tennis ball; that I thought had to be an Indian tool of some sorts. Wrong, I have a stone that at some time in the past was in stone depression at the base of a waterfall and the constant tumbling rounded the stone into a perfect sphere.