South Fork Crooked River

The South Fork Crooked River flows north for about 76 miles through Deschutes and Crook counties before joining Beaver Creek to form the Crooked River proper near Paulina, and BLM-managed land along it — including the well-known Congleton Hollow site about 60 miles east of Prineville — is one of central Oregon's classic limb-cast localities.[^1][^2] These agatized limb casts formed when hot volcanic ash from the Clarno Formation (roughly 38–30 million years old) encased tree branches and stumps; the wood burned out, leaving cavities that later filled with chalcedony, jasper, or other silica minerals.[^3] Most agate here runs clear with frosty banding, and some pieces show blue or green moss-agate coloring — genuinely good material, but it takes digging, not just surface scanning, to find the best pieces.

The South Fork Crooked River area is reached via BLM roads roughly 60 miles east of Prineville, in Crook County near Paulina.[^2] Roads into sites like Congleton Hollow are rugged and can turn muddy in wet weather — a 4WD vehicle is strongly preferable. Note that the first 1.1 miles of Congleton Hollow Road crosses private land; stay on the road and respect posted boundaries until you reach public BLM ground.[^2]

This is dig collecting, not surface picking — limb casts typically sit about 18 inches below the surface, so bring a shovel and digging bar in addition to a rock hammer.[^3] Two separate locations along the South Fork Crooked River on BLM-managed land are documented for this kind of collecting.[^3]

This area is managed by the BLM (Prineville District). Standard BLM personal-use collecting limits apply — 25 pounds per day plus one piece, up to 250 pounds per year, with no power equipment or explosives.[^4] Watch for the private-land stretch at the start of the Congleton Hollow access road, and check current road conditions before heading out, since access can be seasonal and weather-dependent. Official rules: BLM Prineville District, blm.gov.