300 Million Year Old Fern Fossil (pos & neg)

This is a Pecopteris fern fossil from Mazon Creek in Illinois. It's Pennsylvanian in age, or approximately 300 million years old and preserved in an ironstone nodule. Both the positive and negative impression are included.

The Mazon creek deposits are world famous for their finely preserved fossils found within these ironstone nodules. Thousands if not millions of these nodules have been collected over the years from the spoil heaps of abandoned coal mines in the area.