Locality · State land: free permit, no sale
Mazon Creek Pit 11 (Mazonia–Braidwood)
Grundy, Illinois, United States
Pit 11, the former Peabody Coal strip mine that is now the Mazonia–Braidwood State Fish and Wildlife Area, is the classic Mazon Creek collecting site, where surface-hunting for ironstone concretions after winter freeze-thaw still yields ferns and occasionally animals. Collecting is by free state permit and strictly non-commercial, so Mazon Creek material in trade is old stock from the mining decades. The ESCONI club runs field trips and identification days.
| Country | United States |
|---|---|
| State / province | Illinois |
| County | Grundy |
| Land manager / status | Illinois Department of Natural Resources |
| Access | Collecting permit issued free at the site office; open March 1 – September 30 outside hunting season |
| Formations | Mazon Creek (Francis Creek Shale) |
| What is found | Tullimonstrum, Neuropteris, Annularia, Pecopteris, Essexella, shrimp |
| Coordinates (public site) | 41.19, -88.28 |
Rules
A free IDNR fossil-collecting permit is required and must be carried; collecting is limited to surface concretions, no digging, hand tools only, and the material is for personal collections and may not be sold. Scientifically important finds should be reported to the Field Museum or ESCONI.
Source: https://dnr.illinois.gov/parks/park.mazoniabraidwood.html (checked 2026-09-16).
Collecting rules
Elsewhere
Cite this article
Stratum Study. "Mazon Creek Pit 11 (Mazonia–Braidwood)" (Locality). Stratum Study pack 2026.09, as of 2026-09-19. https://stratum.black/study/localities/mazon-creek-pit-11-mazoniabraidwood. Accessed 2026-09-20.
@misc{stratum-mazon-creek-pit-11-mazoniabraidwood,
title = {Mazon Creek Pit 11 (Mazonia–Braidwood)},
author = {{Stratum Study}},
howpublished = {\url{https://stratum.black/study/localities/mazon-creek-pit-11-mazoniabraidwood}},
year = {2026},
note = {Locality article, Stratum Study pack 2026.09, as of 2026-09-19; sources: stratum. Accessed 2026-09-20.}
} Citations carry the pack version and the article's as-of date so they resolve to the same text later. The facts themselves belong to the sources listed below; cite those for the science.