Mazonia-Braidwood State Fish & Wildlife Area (Pit 11) — Rockhounding in Grundy County, Illinois
Updated July 2026
The Mazonia unit preserves the reclaimed spoil of the old Pit 11 coal strip mine, the source of the world-famous Mazon Creek fossil biota and its soft-bodied preservation inside siderite (ironstone) concretions. This is the type ground of the Tully Monster, Tullimonstrum gregarium, named the Illinois state fossil in 1989. It is one of the very few public sites in Illinois where collecting is expressly allowed, under a free permit from the Illinois Department of Natural Resources. Reported finds include concretions with fossils, siderite, tully monster, fern fossils. Below: coordinates, access notes, nearby spots, and trip-planning links.
Mazonia-Braidwood State Fish & Wildlife Area (Pit 11) photos
Public image records connected to this spot or its reported material.
Map showing Mazonia-Braidwood State Fish & Wildlife Area (Pit 11) in Grundy County, Illinois
Quick details
- Access
- Public area
- County
- Grundy County
- State
- Illinois
- Nearest road
- Illinois Route 53
- Postcode
- 60408
- Coordinates
- 41.19750, -88.27080
Land & collecting status
Generally open to casual rockhounding
Most public-tagged spots sit on BLM, U.S. Forest Service, or other federal land where reasonable hand collecting of common rocks and minerals is allowed. Confirm posted rules and active mining claims before you dig.
Public-land rules vary by agency, season, and field office. The RockHoundR app pulls live BLM, USFS, NPS, and tribal overlays so you can see exactly which agency manages the ground at this spot.
Sources & verification
Spot details combine the public RockHoundR location dataset, normalized mineral labels, agency land-status checks in the app, and community submissions. Coordinates are approximate until verified in the field.
Sources: RockHoundR public spot dataset, app land overlays, and local agency review before each trip.
Found at Mazonia-Braidwood State Fish & Wildlife Area (Pit 11)
Each chip opens all spots that produce that material; the encyclopedia link opens the full ID and field guide.
- Concretions With FossilsEncyclopedia →
- SideriteEncyclopedia →
- Tully Monster
- Fern FossilsEncyclopedia →
Nearby rockhounding spots
Other rockhounding spots within driving distance of Mazonia-Braidwood State Fish & Wildlife Area (Pit 11).
- East BrooklynGrundy County, Illinois · 3 mi awayMarcasite, Pyrite
- Coal CityWill County, Illinois · 7 mi awayConcretions With Fossils
- Mazon RiverGrundy County, Illinois · 8 mi awayFossils
- North AuroraKane County, Illinois · 42 mi awayBornite, Calcite, Chalcopyrite
- Bishop HillHenry County, Illinois · 96 mi awayAgate, Jasper
- Rapatee Strip MineTop pick in IllinoisFulton County, Illinois · 104 mi awayPyritized Gastropods
- CordovaTop pick in IllinoisRock Island County, Illinois · 112 mi awayAgate
Across the state line from Mazonia-Braidwood State Fish & Wildlife Area (Pit 11)
Mazonia-Braidwood State Fish & Wildlife Area (Pit 11) is close enough to the Illinois border that the next-closest rockhounding spots are in a neighboring state. Worth knowing if you are already on the road.
Mazonia-Braidwood State Fish & Wildlife Area (Pit 11) FAQ
Why is Mazonia-Braidwood State Fish & Wildlife Area (Pit 11) one of the best rockhounding spots in Illinois?+
Where is Mazonia-Braidwood State Fish & Wildlife Area (Pit 11)?+
What rocks and minerals can you find at Mazonia-Braidwood State Fish & Wildlife Area (Pit 11)?+
Is collecting allowed at Mazonia-Braidwood State Fish & Wildlife Area (Pit 11)?+
How do I get to Mazonia-Braidwood State Fish & Wildlife Area (Pit 11)?+
More rockhounding in Illinois
See all 30 Illinois spots →Open Mazonia-Braidwood State Fish & Wildlife Area (Pit 11) on the map
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