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, jasper, petrified wood, corvusite, 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 164
Coordinates: 38.83695, -109.53102

Geology at Thompson Springs

This spot sits on ground mapped as Salt Wash Member of Morrison Formation that formed roughly 160 to 145 million years ago. Petrified wood typically comes from volcanic ash beds like the ones associated with this ground, where buried forests were slowly replaced by silica.

Mapped unit: Salt Wash Member of Morrison Formation
Age: 160–145 Ma (Late Jurassic)
Elevation: 4,680 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 May. Typical highs run 99°F in midsummer and 40°F in midwinter, with winter lows near 14°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, DEWEY station (13 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 38.83695, -109.53102. Nearest road: CR 164.

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

Thompson Springs is reported to produce Agate, Agatized Clams, Jasper, Petrified Wood, Corvusite, Selenium, Uraninite, Autunite.

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?+

A rock hammer, sturdy gloves, and a padded bag cover petrified wood hunting. Most pieces are surface float, so walking slopes and washes beats digging.

When is the best time to visit Thompson Springs?+

The most comfortable months at Thompson Springs are February to May. 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 38.83695, -109.53102 in Google Maps. The nearest road is CR 164.

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