Rock City Park: Concretion Rockhounding in Ottawa County, Kansas

Quick details

Access

Public area

County

Ottawa County

State

Kansas

Nearest road

North 100th Road

Postcode

67467

Coordinates

39.09271, -97.73910

Geology at Rock City Park

This spot sits on Dakota Formation, mapped as claystone, mudstone, and shale that formed roughly 145 to 100 million years ago. Sedimentary rock like this erodes unevenly, so the most productive collecting is typically along fresh cuts, badland slopes, and active drainages.

Mapped unit

Dakota Formation

Age

145–100 Ma (Early Cretaceous)

Rock types

claystone, mudstone, and shale

Elevation

1,270 ft

Geologic mapping via Macrostrat and the underlying state geological survey maps (CC BY 4.0). Bedrock at the surface can vary within a mapped unit.

Best time to visit Rock City Park

Best months: February to June. Typical highs run 93°F in midsummer and 41°F in midwinter, with winter lows near 18°F.

Climate normals: NOAA 1991-2020 monthlies, MINNEAPOLIS station (3 mi away).

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 Rock City Park

Each chip opens all spots that produce that material; the encyclopedia link opens the full ID and field guide.

• Concretion