Tri-State Marker: Rose Agate Rockhounding in Cimarron County, Oklahoma

Updated June 2026

Tri-State Marker is a mapped rockhounding spot in Cimarron County, Oklahoma. Reported finds include rose agate. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Check locally
County: Cimarron County
State: Oklahoma
Nearest road: E0007 Road
Coordinates: 36.99913, -103.00057

Geology at Tri-State Marker

This spot sits on Dockum Group, mapped as siltstone, conglomerate, and sandstone that formed roughly 235 to 200 million years ago. Tough silica like agate, jasper, and chert typically weathers out of beds like these and collects as float in drainages and on deflation surfaces.

Mapped unit: Dockum Group
Age: 235–200 Ma (Late Triassic)
Rock types: siltstone, conglomerate, and sandstone
Elevation: 4,430 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 Tri-State Marker

Best months: August to June. Typical highs run 93°F in midsummer and 51°F in midwinter, with winter lows near 19°F.

Climate normals: NOAA 1991-2020 monthlies, KENTON station (7 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.

Sources: RockHoundR public spot dataset, app land overlays, and local agency review before each trip.

Found at Tri-State Marker

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

Rose Agate Encyclopedia →

Nearby rockhounding spots

Other rockhounding spots within driving distance of Tri-State Marker.

Carrizozo CreekTop pick in OklahomaCimarron County, Oklahoma · 2 mi awayRose Agate, Agatized Algae, Agatized Cyad Wood

Across the state line from Tri-State Marker

Tri-State Marker is close enough to the Oklahoma border that the next-closest rockhounding spots are in a neighboring state. Worth knowing if you are already on the road.

Tri-State Marker FAQ

Where is Tri-State Marker?+

Tri-State Marker is in Cimarron County, Oklahoma, at 36.99913, -103.00057. Nearest road: E0007 Road.

What rocks and minerals can you find at Tri-State Marker?+

Tri-State Marker is reported to produce Rose Agate.

Is collecting allowed at Tri-State Marker?+

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 Tri-State Marker?+

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 Tri-State Marker?+

The most comfortable months at Tri-State Marker are August to June.

How do I get to Tri-State Marker?+

Open the directions link to navigate to 36.99913, -103.00057 in Google Maps. The nearest road is E0007 Road.

More rockhounding in Oklahoma

See all 36 Oklahoma spots →

Open Tri-State Marker on the map

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