Richardton: Agate & Chalcedony Rockhounding in Stark County, North Dakota

Plan your visit

Generally open to casual rockhounding

County

Stark County

State

North Dakota

Nearest road

42nd Street Southwest

Coordinates

46.80314, -102.30975

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: Surrounding land is largely private ranch and farm ground, so ask the landowner first. The nearest legally open public ground is the Little Missouri National Grassland to the west, under USFS casual-collecting rules. Selenite, agate, and agatized wood weather from Cannonball and Bullion Creek exposures.

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 Richardton

Comfortable months (45 to 90°F highs)

Best months: April to October. Typical highs run 83°F in midsummer and 24°F in midwinter, with winter lows near 8°F.

Climate normals: NOAA 1991-2020 monthlies, RICHARDTON ABBEY station (6 mi away).

Geology at Richardton

This spot sits on Sentinel Butte Formation, mapped as siltstone, claystone, and sandstone 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

Sentinel Butte Formation

Age

66–56 Ma (Paleocene)

Rock types

siltstone, claystone, and sandstone

Elevation

2,350 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