Sioux Falls: Agate & Catlinite Rockhounding in Minnehaha County, South Dakota

Quick details

Access

Public area

County

Minnehaha County

State

South Dakota

Nearest road

East Rice Street

Coordinates

43.58463, -96.66690

Geology at Sioux Falls

This spot sits on ground mapped as chert, shale, and chalk that formed roughly 145 to 66 million years ago. Chert and agate nodules typically form inside carbonate rock like this and weather out as tough, waxy lumps in soils and creek beds.

Age

145–66 Ma (Early Cretaceous to Late Cretaceous)

Rock types

chert, shale, and chalk

Elevation

1,310 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 Sioux Falls

Best months: March to November. Typical highs run 86°F in midsummer and 28°F in midwinter, with winter lows near 9°F.

Climate normals: NOAA 1991-2020 monthlies, SIOUX FALLS station (3 mi away), adjusted for elevation.

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 Sioux Falls

Each chip opens all spots that produce that material; the encyclopedia link opens the full ID and field guide.

• AgateEncyclopedia →
• Catlinite
• JasperEncyclopedia →