Where: Midwest · North America · approx. 41.3, -88.24 (vicinity only)
Why this spot: Mazon Creek concretions (ferns, Tully monster)
What turns up: Pennsylvanian ironstone concretions from the Mazon Creek area preserve soft-bodied plants and animals; collecting is on spoil piles with access limits.
Access: Open / legal.
Open public collecting under BLM or public-land casual-use rules: reasonable personal amounts, hand tools, no claim-jumping, no resale. Confirm current status before you go.
Open in Mudlark Map →
Satellite view, historic-map overlays, tide/flow context and field notes are in the app. Exact research detail is part of Pro.
Pins are approximate by design. This page is historical research, not permission to dig. Check ownership and local law first.