Best spot

Hamilton: Geode Digging in Hancock County, Illinois

Updated July 2026

Hamilton lies on the Mississippi River within the Keokuk geode bed, a Lower Mississippian (Warsaw Formation) zone regarded as one of the finest quartz-geode localities on Earth. Geodes weather from the limestone and shale into area creeks and river gravel, their hollow interiors lined with sparkling quartz and often calcite, pyrite, or sphalerite. The Hamilton-Nauvoo stretch of Hancock County is the Illinois core of a district spanning the Illinois-Iowa-Missouri corner. Reported finds include agate, jasper, geode. Below: coordinates, access notes, nearby spots, and trip-planning links.

Hamilton photos

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

1 photo

Lock and Dam No. 19 on the Mississippi River at the Keokuk-Hamilton crossing, opposite Hamilton, Hancock County, Illinois

Quick details

Access: Public area
County: Hancock County
State: Illinois
Nearest road: South 9th Street
Postcode: 62341
Coordinates: 40.38723, -91.34623

Geology at Hamilton

This spot sits on Warsaw Formation and Salem Limestone, mapped as limestone that formed roughly 345 to 330 million years ago. Limestone country like this is classic geode ground: cavities in the carbonate rock can line themselves with quartz or calcite crystals.

Mapped unit: Warsaw Formation and Salem Limestone
Age: 345–330 Ma (Mississippian)
Rock types: limestone
Elevation: 560 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 Hamilton

Best months: March to November. Typical highs run 85°F in midsummer and 33°F in midwinter, with winter lows near 17°F.

Climate normals: NOAA 1991-2020 monthlies, KEOKUK L&D 19 station (2 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 Hamilton

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 Hamilton.

Across the state line from Hamilton

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

Hamilton FAQ

Where is Hamilton?+

Hamilton is in Hancock County, Illinois, at 40.38723, -91.34623. Nearest road: South 9th Street.

What rocks and minerals can you find at Hamilton?+

Hamilton is reported to produce Agate, Jasper, Geode.

Is collecting allowed at Hamilton?+

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 Hamilton?+

Bring a crack hammer, a chisel, safety glasses, and a bucket. Candidates are rounder and lighter than solid rock; a soil pipe cutter opens them cleaner than a flat smash.

When is the best time to visit Hamilton?+

The most comfortable months at Hamilton are March to November.

How do I get to Hamilton?+

Open the directions link to navigate to 40.38723, -91.34623 in Google Maps. The nearest road is South 9th Street.

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