Cheyenne River: Fairburn Agate Rockhounding in Custer County, South Dakota

Plan your visit

Generally open to casual rockhounding

County

Custer County

State

South Dakota

Coordinates

43.60283, -103.02303

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: The ground here is Buffalo Gap National Grassland (USFS Fall River Ranger District), where personal-use surface collecting of agates is allowed without a permit; commercial collecting is prohibited. The land is a federal and private checkerboard, so collectors should avoid posted private ranch parcels and confirm they are on grassland tracts. River-gravel bars on the navigable channel are also generally open to surface picking.

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 Cheyenne River

Comfortable months (45 to 90°F highs)

Best months: March to November. Typical highs run 90°F in midsummer and 39°F in midwinter, with winter lows near 12°F.

Climate normals: NOAA 1991-2020 monthlies, ORAL station (18 mi away), adjusted for elevation.

Geology at Cheyenne River

This spot sits on ground mapped as Alluvial deposits that formed within roughly the last 3 million years. Gravels like these concentrate whatever survives the river: agate, jasper, and other tough silica typically show up as rounded, waxy stones.

Mapped unit

Alluvial deposits

Age

3 Ma to present (Pleistocene to Holocene)

Elevation

2,740 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.

• BLM Montana-Dakotas rockhounding rules
• Buffalo Gap National Grassland
• South Dakota Geological Survey
• Community submissions reviewed against published agency rules