Cave-In-Rock

Cave-In-Rock sits in Hardin County, Illinois, right on the edge of the Illinois-Kentucky Fluorspar District — the historic source of fluorite, Illinois's state mineral, along with a striking list of associated minerals: barite, galena, sphalerite, witherite, and smithsonite.[1][2] The 55-foot-wide cave itself, carved into a limestone bluff above the Ohio River, is the centerpiece of Cave-In-Rock State Park, established in 1929 and now 204 acres.[2] The catch: this is a state park, and Illinois state parks generally restrict removing natural material, including rocks and minerals — the park protects the cave and bluffs as a scenic/historic feature, not a dig site. The real fluorspar-district collecting opportunities (old mine dumps, fee sites) are elsewhere in Hardin County, not inside the park boundary.

Cave-In-Rock is on the Ohio River in Hardin County, Illinois, accessible via IL-1. The cave itself is reached by a short trail from the park's main area.

UNVERIFIED and likely not permitted within the state park itself — could not confirm current Illinois DNR collecting rules for this specific park (the department's site rules page did not return usable content on fetch). Historic fluorspar mining and mineral collecting happened at mines and dumps scattered through the wider Hardin/Pope County district, not inside protected park land.

Cave-In-Rock State Park is managed by the Illinois Department of Natural Resources.[2] Confirm current collecting rules directly with IDNR (217-782-6302) before assuming any material can be removed — most state parks prohibit taking rocks, minerals, or fossils. If you're after fluorspar-district specimens specifically, look to the wider Hardin County mining district rather than the park itself.