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Hartville: Agate & Moss Agate Rockhounding in Platte County, Wyoming

Public accessBest spot3 mineralsPlatte County, WyomingUpdated October 2026
2 photos
Minerals reported
3
Elevation
4,700 ft
Best months
March to November

Hartville is the southeastern Wyoming choice for Guernsey Limestone chalcedony, including moss agate, dendritic agate, stalactitic agate, and youngite noted by WSGS. Its appeal is the combination of lapidary-grade silica and mining-district geology in a part of the state outside the central Sweetwater jade and agate belt. Reported finds include agate, moss agate, chalcedony. Below: coordinates, access notes, nearby spots, and trip-planning links.

Plan your visit

Generally open to casual rockhounding

State
Wyoming
Nearest road
Lakeside Road
Postcode
82214
Get directionsView on Google Maps

Coordinates are approximate. Confirm the exact ground in the RockHoundR app, where land overlays show which agency manages the area.

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.

Access note: The Hartville Uplift includes old mine ground, private parcels, and public land; avoid workings and verify open access before collecting. BLM records active mining claims in this area. Collecting from inside an active claim needs the claim holder's permission.

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.

Best time to visit Hartville

Comfortable months (45 to 90°F highs)

Best months: March to November. Typical highs run 88°F in midsummer and 38°F in midwinter, with winter lows near 13°F.

Climate normals: NOAA 1991-2020 monthlies, GUERNSEY DAM #2 station (2 mi away), adjusted for elevation.

Geology at Hartville

This spot sits on ground mapped as Divisions 4 and 5, Hartville Formation that formed roughly 325 to 300 million years ago. Tough silica like agate and jasper typically survives weathering and collects as float in drainages and gravel.

Mapped unit
Divisions 4 and 5, Hartville Formation
Age
325–300 Ma (Pennsylvanian)
Elevation
4,700 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.

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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:

Found at Hartville

Each name 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 Hartville.

Across the state line from Hartville

Hartville 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.

Hartville FAQ

Where is Hartville?+
Hartville is in Platte County, Wyoming, at 42.32213, -104.74818. Nearest road: Lakeside Road.
What rocks and minerals can you find at Hartville?+
Hartville is reported to produce Agate, Moss Agate, Chalcedony.
Is collecting allowed at Hartville?+
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 Hartville?+
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 Hartville?+
The most comfortable months at Hartville are March to November.
How do I get to Hartville?+
Open the directions link to navigate to 42.32213, -104.74818 in Google Maps. The nearest road is Lakeside Road.

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