Black Hawk County: Coldwater Agate Rockhounding in Black Hawk County, Iowa
Updated July 2026
The Cedar River valley through Black Hawk County is the home ground of the Iowa coldwater agate, a pale blue-gray to cream banded agate weathered from Devonian limestone and reworked into the river gravels. It occurs alongside true Lake Superior agates carried in by glaciers, giving the local bars two distinct agate types. The Cedar River constantly refreshes its gravel, so productive ground shifts with each season. Reported finds include coldwater agate. Below: coordinates, access notes, nearby spots, and trip-planning links.
Black Hawk County photos
Public image records connected to this spot or its reported material.
Map showing Black Hawk County in Black Hawk County, Iowa
Quick details
- Access
- Public area
- County
- Black Hawk County
- State
- Iowa
- Nearest road
- North Elk Run Road
- Postcode
- 50703
- Coordinates
- 42.52178, -92.25494
Geology at Black Hawk County
This spot sits on ground mapped as Cedar Valley Group that formed roughly 390 to 370 million years ago. Tough silica like agate and jasper typically survives weathering and collects as float in drainages and gravel.
- Mapped unit
- Cedar Valley Group
- Age
- 390–370 Ma (Middle Devonian to Late Devonian)
- Elevation
- 910 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 Black Hawk County
Best months: March to November. Typical highs run 85°F in midsummer and 28°F in midwinter, with winter lows near 11°F.
Climate normals: NOAA 1991-2020 monthlies, WATERLOO MUNI AP 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 Black Hawk 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 Black Hawk County.
- Riverview Recreation AreaBlack Hawk County, Iowa · 4 mi awayGeode
- La Porte CityBlack Hawk County, Iowa · 14 mi awayAgate
- BrandonBuchanan County, Iowa · 20 mi awayGeode, Fossils
- Bremer CountyBremer County, Iowa · 21 mi awayColdwater Agate
- Shell RockButler County, Iowa · 22 mi awayLake Superior Agate
- Benton CountyBenton County, Iowa · 27 mi awayColdwater Agate
- Fayette CountyFayette County, Iowa · 38 mi awayLake Superior Agate
- Steamboat RiverTop pick in IowaHardin County, Iowa · 42 mi awayGeode
Across the state line from Black Hawk County
Black Hawk County 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.
Black Hawk County FAQ
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More rockhounding in Iowa
See all 49 Iowa spots →Open Black Hawk County on the map
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