White Rock: Thundereggs & Agate Rockhounding in Crook County, Oregon

Quick details

Access

Public area

County

Crook County

State

Oregon

Nearest road

White Rock Spring Road

Coordinates

44.42449, -120.54655

Geology at White Rock

This spot sits on John Day/Clarno Group; John Day Formation, mapped as ash-flow tuff, lapilli pumice, dacite tuff, and rhyolite tuff that formed roughly 56 to 23 million years ago. Volcanic ground like this is where agate, jasper, and other chalcedony typically form, filling old gas pockets and fracture seams in the flow rock.

Mapped unit

John Day/Clarno Group; John Day Formation

Age

56–23 Ma (Eocene to Oligocene)

Rock types

ash-flow tuff, lapilli pumice, dacite tuff, and rhyolite tuff

Elevation

5,600 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 White Rock

Best months: March to October. Typical highs run 77°F in midsummer and 33°F in midwinter, with winter lows near 15°F.

Climate normals: NOAA 1991-2020 monthlies, PRINEVILLE station (17 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 Oregon/Washington — Rockhounding & mineral material
• Oregon Department of Geology and Mineral Industries (DOGAMI)
• Oregon Parks and Recreation Department — beach collecting rules
• Community submissions reviewed against published agency rules

Found at White Rock

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

• ThundereggsEncyclopedia →
• AgateEncyclopedia →
• ChalcedonyEncyclopedia →
• OpalEncyclopedia →