San Rafael Swell: Jasper & Agate Rockhounding in Emery County, Utah

Plan your visit

Generally open to casual rockhounding

County

Emery County

State

Utah

Nearest road

Green River Cutoff

Coordinates

39.20346, -110.37129

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.

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 San Rafael Swell

Comfortable months (45 to 90°F highs)

Best months: February to June. Typical highs run 94°F in midsummer and 44°F in midwinter, with winter lows near 28°F.

Climate normals: NOAA 1991-2020 monthlies, SUNNYSIDE CITY station (24 mi away), adjusted for elevation.

Geology at San Rafael Swell

This spot sits on ground mapped as Tununk Member of Mancos Shale that formed roughly 100 to 66 million years ago. Tough silica like agate, jasper, and chert typically weathers out of beds like these and collects as float in drainages and on deflation surfaces.

Mapped unit

Tununk Member of Mancos Shale

Age

100–66 Ma (Late Cretaceous)

Elevation

4,840 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.

State guidance last verified: April 1, 2026

• BLM Utah, Rockhounding overview
• Utah Geological Survey, collecting guidelines
• SITLA, surface use rules
• Community submissions reviewed against published agency rules