Poison Creek: Common Opal Rockhounding in Custer County, Idaho

Updated June 2026

Poison Creek is a mapped rockhounding spot in Custer County, Idaho. Reported finds include common opal. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Public area
County: Custer County
State: Idaho
Coordinates: 43.71710, -113.65649

Geology at Poison Creek

This spot sits on Alluvium of tributary streams, mapped as silty sand;silt;clay;gravel that formed within roughly the last 129,000 years. Gravels like these concentrate whatever survives the river: agate, jasper, and other tough silica typically show up as rounded, waxy stones.

Mapped unit: Alluvium of tributary streams
Age: < 1 Ma (Late Pleistocene to Holocene)
Rock types: silty sand;silt;clay;gravel
Elevation: 6,710 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 Poison Creek

Best months: April to October. Typical highs run 80°F in midsummer and 27°F in midwinter, with winter lows near 6°F.

Climate normals: NOAA 1991-2020 monthlies, MACKAY LOST RVR RS station (14 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

Idaho Panhandle National Forests — Emerald Creek
Idaho Geological Survey
Spencer Opal Mines (fee-dig operator)
Community submissions reviewed against published agency rules

Found at Poison Creek

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

Common Opal Encyclopedia →

Nearby rockhounding spots

Other rockhounding spots within driving distance of Poison Creek.

Poison Creek FAQ

Where is Poison Creek?+

Poison Creek is in Custer County, Idaho, at 43.71710, -113.65649.

What rocks and minerals can you find at Poison Creek?+

Poison Creek is reported to produce Common Opal.

Is collecting allowed at Poison Creek?+

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 Poison Creek?+

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 Poison Creek?+

The most comfortable months at Poison Creek are April to October.

How do I get to Poison Creek?+

Open the directions link to navigate to 43.71710, -113.65649 in Google Maps. Some spots are remote, so check road conditions before driving out.

More rockhounding in Idaho

See all 115 Idaho spots →

Open Poison Creek on the map

Use the RockHoundR app for live land overlays, weather, geology, directions, and saved finds.