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Lower Inmaha River: Agate & Prase Rockhounding in Wallowa County, Oregon

Updated June 2026

Lower Inmaha River is a mapped rockhounding spot in Wallowa County, Oregon. Reported finds include agate, prase. Below: coordinates, access notes, nearby spots, and trip-planning links.

Map showing Lower Inmaha River in Wallowa County, Oregon

Quick details

Access
Public area
State
Oregon
Nearest road
Forest Road 3955

Geology at Lower Inmaha River

This spot sits on Columbia River Basalt Group; Grande Ronde Basalt; Reversed magnetostratigraphic unit 1, mapped as basalt flows and plagioclase phenocrysts that formed roughly 23 to 5 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
Columbia River Basalt Group; Grande Ronde Basalt; Reversed magnetostratigraphic unit 1
Age
23–5 Ma (Miocene)
Rock types
basalt flows and plagioclase phenocrysts
Elevation
3,710 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 Lower Inmaha River

Best months: March to October. Typical highs run 81°F in midsummer and 37°F in midwinter, with winter lows near 21°F.

Climate normals: NOAA 1991-2020 monthlies, JOSEPH station (20 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:

Found at Lower Inmaha River

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 Lower Inmaha River.

Across the state line from Lower Inmaha River

Lower Inmaha River is close enough to the Oregon border that the next-closest rockhounding spots are in a neighboring state. Worth knowing if you are already on the road.

Lower Inmaha River FAQ

Where is Lower Inmaha River?+
Lower Inmaha River is in Wallowa County, Oregon, at 45.20361, -116.86702. Nearest road: Forest Road 3955.
What rocks and minerals can you find at Lower Inmaha River?+
Lower Inmaha River is reported to produce Agate, Prase.
Is collecting allowed at Lower Inmaha River?+
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 Lower Inmaha River?+
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 Lower Inmaha River?+
The most comfortable months at Lower Inmaha River are March to October.
How do I get to Lower Inmaha River?+
Open the directions link to navigate to 45.20361, -116.86702 in Google Maps. The nearest road is Forest Road 3955.

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