Boulder Creek: Pyrite Rockhounding in Linn County, Oregon

Quick details

Access

Check locally

County

Linn County

State

Oregon

Nearest road

Boulder Creek Road

Coordinates

44.56960, -122.38460

Geology at Boulder Creek

This spot sits on Little Butte Volcanics, mapped as autoclastic breccia, bluish gray, purplish red; andesite, basalt clasts, andesite flows, bluish gray; fe-ti oxides blebs; zones: andesine compositional zoning; calcic andesine, clinopyroxene, orthopyroxene phenocrysts; alteration: andesine altered to calcite, pyroxene altered to calcite, chlorite, montmorillonite; matrix: plagioclase feldspar microlites, basaltic andesite flows, medium to dark gray; calcic andesine, orthopyroxene phenocrysts; alteration: andesine partially altered to clay minerals, orthopyroxene replaced by chlorite and calcite, iddingsite, quartz, ilmenite; zones: zoned calcic andesine; fe-ti oxides phenocrysts; fe-ti oxides blebs; matrix: andesine microlites, brown glass, fe-ti oxides, and orthopyroxene that formed roughly 34 to 5 million years ago. Volcanic ground like this weathers into rocky slopes and float, and fresh exposures in cuts and drainages are usually the most productive places to look.

Mapped unit

Little Butte Volcanics

Age

34–5 Ma (Oligocene to Miocene)

Rock types

autoclastic breccia, bluish gray, purplish red; andesite, basalt clasts, andesite flows, bluish gray; fe-ti oxides blebs; zones: andesine compositional zoning; calcic andesine, clinopyroxene, orthopyroxene phenocrysts; alteration: andesine altered to calcite, pyroxene altered to calcite, chlorite, montmorillonite; matrix: plagioclase feldspar microlites, basaltic andesite flows, medium to dark gray; calcic andesine, orthopyroxene phenocrysts; alteration: andesine partially altered to clay minerals, orthopyroxene replaced by chlorite and calcite, iddingsite, quartz, ilmenite; zones: zoned calcic andesine; fe-ti oxides phenocrysts; fe-ti oxides blebs; matrix: andesine microlites, brown glass, fe-ti oxides, and orthopyroxene

Elevation

1,980 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 Boulder Creek

Best months: March to November. Typical highs run 78°F in midsummer and 41°F in midwinter, with winter lows near 34°F.

Climate normals: NOAA 1991-2020 monthlies, DETROIT DAM station (12 mi away), adjusted for elevation.

Land & collecting status

Confirm rules before collecting

Land status here is not confirmed. Verify with the managing agency before collecting — federal, state, and tribal rules differ.

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 Boulder Creek

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

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