I recently went up to a place named Dinosaur Park, in Laurel Maryland. Mostly triassic aged stuff.

The place was originally set up to be an iron mine, and the minors started digging up bones. This location

is famous for the discovery of the Astrodon a large Sauropod.

The images I have inserted are pictures of carbonized pieces of fern. In more common terms, it's coal.

Roughly 120 million years old coal. Some of the coal still has iron traces on it.