Ada County: Agate & Chalcedony Rockhounding in Ada County, Idaho

Quick details

Access

Public area

County

Ada County

State

Idaho

Nearest road

South Pleasant Valley Road

Coordinates

43.38450, -116.23256

Geology at Ada County

This spot sits on Idaho Group and other fluvial, lacustrine, and eolian sediments in the NE part of the Murphy quadrangle, mapped as silt;sand;clay;gravel that formed within roughly the last 5 million years. Petrified wood typically travels as tough float, and worked gravels like these are exactly where weathered pieces tend to collect.

Mapped unit

Idaho Group and other fluvial, lacustrine, and eolian sediments in the NE part of the Murphy quadrangle

Age

5 Ma to present (Pliocene to Pleistocene)

Rock types

silt;sand;clay;gravel

Elevation

2,910 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 Ada County

Best months: February to June. Typical highs run 93°F in midsummer and 40°F in midwinter, with winter lows near 24°F.

Climate normals: NOAA 1991-2020 monthlies, SWAN FALLS PH station (12 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 Ada County

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

• AgateEncyclopedia →
• ChalcedonyEncyclopedia →
• JasperEncyclopedia →
• Petrified WoodEncyclopedia →
• Opalized WoodEncyclopedia →