Cooney Hills: Garnet Rockhounding in Platte County, Wyoming

Updated June 2026

Cooney Hills is a mapped rockhounding spot in Platte County, Wyoming. Reported finds include garnet. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Public area
County: Platte County
State: Wyoming
Coordinates: 41.98159, -105.11383

Geology at Cooney Hills

This spot sits on Granite gneiss, mapped as gneiss that formed roughly 4030 to 2500 million years ago. Metamorphic rock like this is where garnet, staurolite, and kyanite typically grow as the rock recrystallizes under heat and pressure.

Mapped unit: Granite gneiss
Age: 4030–2500 Ma (Archean)
Rock types: gneiss
Elevation: 5,520 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 Cooney Hills

Best months: March to November. Typical highs run 87°F in midsummer and 40°F in midwinter, with winter lows near 13°F.

Climate normals: NOAA 1991-2020 monthlies, WHEATLAND 4N 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

BLM Wyoming
Wyoming State Geological Survey
Fossil Butte National Monument
Community submissions reviewed against published agency rules

Found at Cooney Hills

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

Garnet Encyclopedia →

Nearby rockhounding spots

Other rockhounding spots within driving distance of Cooney Hills.

Across the state line from Cooney Hills

Cooney Hills is close enough to the Wyoming border that the next-closest rockhounding spots are in a neighboring state. Worth knowing if you are already on the road.

Cooney Hills FAQ

Where is Cooney Hills?+

Cooney Hills is in Platte County, Wyoming, at 41.98159, -105.11383.

What rocks and minerals can you find at Cooney Hills?+

Cooney Hills is reported to produce Garnet.

Is collecting allowed at Cooney Hills?+

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. Always confirm current rules with the managing agency before a trip.

What tools should I bring to Cooney Hills?+

A rock hammer, a sieve, and a small shovel work well for garnet-type minerals, which concentrate as resistant grains in soils and creek gravels.

When is the best time to visit Cooney Hills?+

The most comfortable months at Cooney Hills are March to November.

How do I get to Cooney Hills?+

Open the directions link to navigate to 41.98159, -105.11383 in Google Maps. Some spots are remote, so check road conditions before driving out.

More rockhounding in Wyoming

See all 82 Wyoming spots →

Open Cooney Hills on the map

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