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.
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.