Mazon Creek nodule
Fossil
Also called Mazon Creek concretion and Ironstone nodule
About it
Ironstone concretions from Pennsylvanian rocks of northeastern Illinois that split to show ferns, shrimp, jellyfish, worms, and rarely the Tully monster, Illinois's state fossil. Collectors freeze and thaw them to split them.
- Type
- Fossil (other)
- Group
- Concretion (plants and animals)
- Colours
- red-brown, tan, grey, dark fossil
- Transparency
- opaque
- Periods
- Carboniferous
Typical values: real specimens vary. For more, see mindat.org.