Thompson Springs: Agate & Agatized Clams Rockhounding in Grand County, Utah

Updated June 2026

Thompson Springs is a mapped rockhounding spot in Grand County, Utah. Reported finds include agate, agatized clams, anhydrite, carnotite, gypsum, and more. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Public area
County: Grand County
State: Utah
Nearest road: CR 146
Coordinates: 38.86572, -109.70446

Geology at Thompson Springs

This spot sits on ground mapped as Cedar Mountain Formation that formed roughly 115 to 100 million years ago. Tough silica like agate and jasper typically survives weathering and collects as float in drainages and gravel.

Mapped unit: Cedar Mountain Formation
Age: 115–100 Ma (Early Cretaceous)
Elevation: 4,950 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 Thompson Springs

Best months: February to June. Typical highs run 95°F in midsummer and 37°F in midwinter, with winter lows near 16°F. Summer heat here is intense, so carry more water than you think you need and work the early morning.

Climate normals: NOAA 1991-2020 monthlies, MOAB CANYONLAND AP station (9 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.

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

Found at Thompson Springs

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

Nearby rockhounding spots

Other rockhounding spots within driving distance of Thompson Springs.

Thompson Springs FAQ

Where is Thompson Springs?+

Thompson Springs is in Grand County, Utah, at 38.86572, -109.70446. Nearest road: CR 146.

What rocks and minerals can you find at Thompson Springs?+

Thompson Springs is reported to produce Agate, Agatized Clams, Anhydrite, Carnotite, Gypsum, Jasper, Jasperized Dinosaur Bone, Petrified Wood.

Is collecting allowed at Thompson Springs?+

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. Always confirm current rules with the managing agency before a trip.

What tools should I bring to Thompson Springs?+

Most agate and jasper is surface float: bring a spray bottle, a pick or small shovel, and a sturdy bag. Wet stones show their banding and translucence.

When is the best time to visit Thompson Springs?+

The most comfortable months at Thompson Springs are February to June. Summer heat here is intense, so carry more water than you think you need and work the early morning.

How do I get to Thompson Springs?+

Open the directions link to navigate to 38.86572, -109.70446 in Google Maps. The nearest road is CR 146.

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