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Grundy County: Fossil Hunting in Grundy County, Missouri

Updated June 2026

Grundy County rounds out the cluster of glaciated northern Missouri counties that yield ice-transported Lake Superior agates, with mindat documenting Lake Superior agate from the county. Its creeks and the Thompson and Weldon river gravels rework glacial drift, freeing agate, jasper, and petrified wood. The material is the same banded, tumble-rounded agate prized by Midwest collectors. Reported finds include lake superior agate, jasper, fossils, petrified wood. Below: coordinates, access notes, nearby spots, and trip-planning links.

Grundy County photos

Public image records connected to this spot or its reported material.

1 photo

A polished Lake Superior agate with banded fortification structure, the same tumble rounded ice transported agate documented from Grundy County glacial drift and stream gravels.

Quick details

Access: Public area
County: Grundy County
State: Missouri
Coordinates: 40.11964, -93.52957

Geology at Grundy County

This spot sits on Cherokee Group - Cabaniss Subgroup, Krebs Subgroup, mapped as shale, sandstone, and siltstone that formed roughly 325 to 300 million years ago. Sedimentary layers like these are where fossils are typically preserved, and fresh exposures after rain or in active cuts tend to produce best.

Mapped unit: Cherokee Group - Cabaniss Subgroup, Krebs Subgroup
Age: 325–300 Ma (Pennsylvanian)
Rock types: shale, sandstone, and siltstone
Elevation: 790 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 Grundy County

Best months: March to November. Typical highs run 89°F in midsummer and 35°F in midwinter, with winter lows near 16°F.

Climate normals: NOAA 1991-2020 monthlies, TRENTON 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 Grundy County

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 Grundy County.

Across the state line from Grundy County

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

Grundy County FAQ

Where is Grundy County?+

Grundy County is in Grundy County, Missouri, at 40.11964, -93.52957.

What rocks and minerals can you find at Grundy County?+

Grundy County is reported to produce Lake Superior Agate, Jasper, Fossils, Petrified Wood.

Is collecting allowed at Grundy County?+

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 Grundy County?+

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 Grundy County?+

The most comfortable months at Grundy County are March to November.

How do I get to Grundy County?+

Open the directions link to navigate to 40.11964, -93.52957 in Google Maps. Some spots are remote, so check road conditions before driving out.

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