Brown County State Park

Brown County State Park is Indiana's largest state park, sitting on the Knobstone Escarpment in south-central Indiana — steep, forested hills and valleys cut into siltstone of the Borden Group, with secondary limestone, dolomite, and chert layers dating back over 330 million years to a massive ancient river delta [1]. It's genuinely good geology. It is not, however, a place to collect anything: Indiana bans rock and mineral collecting in all state parks, nature preserves, and state forests outright [2]. If the DB's geode/marcasite/aragonite/quartz specimen list is what brought you here, the honest answer is that this exact park isn't where to swing a rock hammer — nearby unprotected ground in Brown County is.

The park is off Indiana State Road 46, near Nashville, Indiana, in Brown County — well-marked, developed state park with standard vehicle access and an entrance fee.

None. Do not collect rock, mineral, or geode material inside Brown County State Park.

Indiana prohibits collecting in all state parks, nature preserves, and state forests, no exceptions noted [2]. If you want to legally look for the geode material this area is known for, the sourced alternative locations outside the park are Beanblossom (in Brown County) and Bear Creek near Trevlac, along with roadside exposures on Indiana State Road 45 and Beanblossom/Blummets creeks [2] — all of which are separate from the state park and would need their own land-status check before collecting. The Hoosier National Forest, which touches Monroe, Lawrence, and Brown counties, allows surface collecting for personal use under 36 CFR 261.9 on the National Forest portions, distinct from the state park [2].