Killdeer: Knife River Flint Rockhounding in Dunn County, North Dakota

Plan your visit

Generally open to casual rockhounding

County

Dunn County

State

North Dakota

Nearest road

County Road 5

Postcode

58541

Coordinates

47.15371, -102.05717

Coordinates are approximate. Confirm the exact ground in the RockHoundR app, where land overlays show which agency manages the area.

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.

Access note: Knife River flint occurs mostly on private ranchland; get landowner permission, and collect only unworked cobbles. Flaked or worked pieces are protected artifacts under state and federal law and must be left in place. The historic quarry sites (Lynch Quarry National Historic Landmark, Crowley Flint Quarry State Historic Site) are closed to collecting. Unworked float can also be found on the Little Missouri National Grassland under USFS rules.

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.

Best time to visit Killdeer

Comfortable months (45 to 90°F highs)

Best months: April to October. Typical highs run 85°F in midsummer and 23°F in midwinter, with winter lows near 3°F.

Climate normals: NOAA 1991-2020 monthlies, BEULAH 1 W station (15 mi away).

Geology at Killdeer

This spot sits on Sentinel Butte Formation, mapped as siltstone, claystone, and sandstone that formed roughly 66 to 56 million years ago. Sedimentary rock like this erodes unevenly, so the most productive collecting is typically along fresh cuts, badland slopes, and active drainages.

Mapped unit

Sentinel Butte Formation

Age

66–56 Ma (Paleocene)

Rock types

siltstone, claystone, and sandstone

Elevation

1,850 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.

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.

• North Dakota Geological Survey
• Dakota Prairie Grasslands
• North Dakota Parks and Recreation rules
• Community submissions reviewed against published agency rules