Polka Dot Agate Mine: Polka Dot Agate & Thundereggs Rockhounding in Jefferson County, Oregon

Updated August 2026

Polka Dot Agate Mine is a mapped rockhounding spot in Jefferson County, Oregon. Reported finds include polka dot agate, thundereggs. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Check locally
County: Jefferson County
State: Oregon
Nearest road: Northeast Pony Butte Road
Coordinates: 44.75868, -120.83032

Geology at Polka Dot Agate Mine

This spot sits on John Day/Clarno Group; John Day Formation, mapped as ash-flow tuff and na sanidine quartz oligoclase phenocrysts that formed roughly 56 to 23 million years ago. Volcanic ground like this is where agate, jasper, and other chalcedony typically form, filling old gas pockets and fracture seams in the flow rock.

Mapped unit: John Day/Clarno Group; John Day Formation
Age: 56–23 Ma (Eocene to Oligocene)
Rock types: ash-flow tuff and na sanidine quartz oligoclase phenocrysts
Elevation: 3,000 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 Polka Dot Agate Mine

Best months: February to November. Typical highs run 87°F in midsummer and 43°F in midwinter, with winter lows near 26°F.

Climate normals: NOAA 1991-2020 monthlies, ANTELOPE 6 SSW station (6 mi away).

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 Polka Dot Agate Mine

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 Polka Dot Agate Mine.

Across the state line from Polka Dot Agate Mine

Polka Dot Agate Mine is close enough to the Oregon border that the next-closest rockhounding spots are in a neighboring state. Worth knowing if you are already on the road.

Polka Dot Agate Mine FAQ

Where is Polka Dot Agate Mine?+

Polka Dot Agate Mine is in Jefferson County, Oregon, at 44.75868, -120.83032. Nearest road: Northeast Pony Butte Road.

What rocks and minerals can you find at Polka Dot Agate Mine?+

Polka Dot Agate Mine is reported to produce Polka Dot Agate, Thundereggs.

Is collecting allowed at Polka Dot Agate Mine?+

Confirm rules before collecting. Land status here is not confirmed. Verify with the managing agency before collecting — federal, state, and tribal rules differ. Always confirm current rules with the managing agency before a trip.

What tools should I bring to Polka Dot Agate Mine?+

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 Polka Dot Agate Mine?+

The most comfortable months at Polka Dot Agate Mine are February to November.

How do I get to Polka Dot Agate Mine?+

Open the directions link to navigate to 44.75868, -120.83032 in Google Maps. The nearest road is Northeast Pony Butte Road.

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