Charlie needed some cash and sold these to me. He found these around our area of central Indiana. He then moved to west Indiana. These were found over ten years ago.
conchocton, notice how the 'lightning' moves down the serrated edge
We get Attica "Indiana Green" around here some. Neat stuff. I looked for the source once but never found it. I heard it was removed and crushed in the 30's for road gravel. Gary