Cedar Creek: Silicified Coral & Calcified Coral Rockhounding in Mahaska County, Iowa

Updated June 2026

Cedar Creek is a mapped rockhounding spot in Mahaska County, Iowa. Reported finds include silicified coral, calcified coral. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Public area
County: Mahaska County
State: Iowa
Nearest road: 335th Street
Coordinates: 41.16780, -92.45991

Geology at Cedar Creek

This spot sits on ground mapped as Pella Fm and St. Louis Fm that formed roughly 340 to 325 million years ago. Fossils here are typically found in fresh exposures, where erosion keeps bringing new material to the surface.

Mapped unit: Pella Fm and St. Louis Fm
Age: 340–325 Ma (Mississippian)
Elevation: 780 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 Cedar Creek

Best months: March to November. Typical highs run 86°F in midsummer and 32°F in midwinter, with winter lows near 14°F.

Climate normals: NOAA 1991-2020 monthlies, OTTUMWA IND AP station (5 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 Cedar Creek

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

Nearby rockhounding spots

Other rockhounding spots within driving distance of Cedar Creek.

Across the state line from Cedar Creek

Cedar Creek is close enough to the Iowa border that the next-closest rockhounding spots are in a neighboring state. Worth knowing if you are already on the road.

Cedar Creek FAQ

Where is Cedar Creek?+

Cedar Creek is in Mahaska County, Iowa, at 41.16780, -92.45991. Nearest road: 335th Street.

What rocks and minerals can you find at Cedar Creek?+

Cedar Creek is reported to produce Silicified Coral, Calcified Coral.

Is collecting allowed at Cedar Creek?+

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. Always confirm current rules with the managing agency before a trip.

What tools should I bring to Cedar Creek?+

A rock hammer, a cold chisel, safety glasses, and newspaper or foam for wrapping finds cover most fossil ground. A trowel and a sieve help in soft exposures.

When is the best time to visit Cedar Creek?+

The most comfortable months at Cedar Creek are March to November.

How do I get to Cedar Creek?+

Open the directions link to navigate to 41.16780, -92.45991 in Google Maps. The nearest road is 335th Street.

More rockhounding in Iowa

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Open Cedar Creek on the map

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