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Horse Heaven Hills: Opalized Wood Rockhounding in Benton County, Washington

Updated June 2026

Horse Heaven Hills is a mapped rockhounding spot in Benton County, Washington. Reported finds include opalized wood. Below: coordinates, access notes, nearby spots, and trip-planning links.

Map showing Horse Heaven Hills in Benton County, Washington

Quick details

Access
Public area
Nearest road
Sellards Road

Geology at Horse Heaven Hills

This spot sits on Elephant Mountain Member, Saddle Mountains Basalt, mapped as basalt flows (elephant mountain member [crb and smb]) that formed roughly 23 to 5 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
Elephant Mountain Member, Saddle Mountains Basalt
Age
23–5 Ma (Miocene)
Rock types
basalt flows (elephant mountain member [crb and smb])
Elevation
1,560 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 Horse Heaven Hills

Best months: March to November. Typical highs run 88°F in midsummer and 38°F in midwinter, with winter lows near 24°F.

Climate normals: NOAA 1991-2020 monthlies, PROSSER station (6 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 Horse Heaven Hills

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 Horse Heaven Hills.

Across the state line from Horse Heaven Hills

Horse Heaven Hills is close enough to the Washington border that the next-closest rockhounding spots are in a neighboring state. Worth knowing if you are already on the road.

Horse Heaven Hills FAQ

Where is Horse Heaven Hills?+
Horse Heaven Hills is in Benton County, Washington, at 46.13160, -119.84629. Nearest road: Sellards Road.
What rocks and minerals can you find at Horse Heaven Hills?+
Horse Heaven Hills is reported to produce Opalized Wood.
Is collecting allowed at Horse Heaven Hills?+
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 Horse Heaven Hills?+
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 Horse Heaven Hills?+
The most comfortable months at Horse Heaven Hills are March to November.
How do I get to Horse Heaven Hills?+
Open the directions link to navigate to 46.13160, -119.84629 in Google Maps. The nearest road is Sellards Road.

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