Ugly Rocks Can Contain Beautiful Treasures

From the outward appearance of certain ironstone or siderite nodules, they might seem to be ugly-looking dirty rocks, but they often hide beautiful treasures inside.

- PALEO JOE

Siderite or ironstone concretions from the area called Mazonia near Braidville, Illinois, often contain a rich diversity of plants...and animals. These plants and creatures once lived in the subtropical jungles, swamps, deltas, and forests in the Illinois Basin of Eastern Central Illinois.

The area around Mazonia is known as a Lagerstatte (in German), which loosely translated means “resting place.” To paleontologists and scientists, it is an area with spectacular preservation of the flora and fauna of an ecosystem.

The Mazon Creek flora and fauna from the Pennsylvanian Sub-Period also called the Age of Plants, are some of the best-known and most highly prized fossils. The Pennsylvanian lasted from some 323.2 million years ago to 298.9 million years ago. During this time, the area contained swamps filled with scale trees, seed ferns, true ferns, horsetails, the first emergence of conifers, and other ground plants. One can imagine these hot, steamy jungles were filled with large ferns and primitive plants. The swamps were full of life scurrying and swimming about. As plants fall onto the rich soil or into the water, they are quickly buried. The process that formed siderite nodules began with decomposition of the plant and animal remains that produced carbon dioxide (CO2) that mixed with the iron in solution from iron-rich groundwater.