Union: Geode Digging in Hardin County, Iowa

Updated June 2026

Union is a mapped rockhounding spot in Hardin County, Iowa. Reported finds include geode. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Public area
County: Hardin County
State: Iowa
Nearest road: 305th Street
Postcode: 50258
Coordinates: 42.25402, -93.05812

Geology at Union

This spot sits on ground mapped as Augusta Group that formed roughly 355 to 330 million years ago. Geodes typically weather free of their host rock and collect as rounded float in soils and drainages.

Mapped unit: Augusta Group
Age: 355–330 Ma (Mississippian)
Elevation: 940 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 Union

Best months: March to November. Typical highs run 84°F in midsummer and 26°F in midwinter, with winter lows near 9°F.

Climate normals: NOAA 1991-2020 monthlies, ELDORA station (8 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 Union

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

Geode Encyclopedia →

Nearby rockhounding spots

Other rockhounding spots within driving distance of Union.

Union FAQ

Where is Union?+

Union is in Hardin County, Iowa, at 42.25402, -93.05812. Nearest road: 305th Street.

What rocks and minerals can you find at Union?+

Union is reported to produce Geode.

Is collecting allowed at Union?+

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 Union?+

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 Union?+

The most comfortable months at Union are March to November.

How do I get to Union?+

Open the directions link to navigate to 42.25402, -93.05812 in Google Maps. The nearest road is 305th Street.

More rockhounding in Iowa

See all 49 Iowa spots →

Open Union on the map

Use the RockHoundR app for live land overlays, weather, geology, directions, and saved finds.