Little Missouri River: Montana Moss Agate & Jasper Rockhounding in McKenzie County, North Dakota

Plan your visit

Generally open to casual rockhounding

County

McKenzie County

State

North Dakota

Coordinates

47.52395, -103.45211

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: Collect on the surrounding Little Missouri National Grassland under USFS casual-collecting rules (hand tools, personal use, no vertebrate fossils). The Little Missouri is a non-navigable river, so its bed and banks are privately owned where they cross private ranchland; obtain landowner permission off the grassland. No collecting inside Theodore Roosevelt National Park.

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 Little Missouri River

Comfortable months (45 to 90°F highs)

Best months: April to October. Typical highs run 85°F in midsummer and 24°F in midwinter, with winter lows near 2°F.

Climate normals: NOAA 1991-2020 monthlies, WATFORD CITY 14S station (10 mi away).

Geology at Little Missouri River

This spot sits on Bullion Creek Formation, mapped as claystone and siltstone that formed roughly 66 to 56 million years ago. Sedimentary beds like these are the typical host for petrified and silicified wood, which weathers out as durable float on slopes and in washes.

Mapped unit

Bullion Creek Formation

Age

66–56 Ma (Paleocene)

Rock types

claystone and siltstone

Elevation

1,980 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