Sweetwater River: Agate Rockhounding in Fremont County, Wyoming
- Mineral reported
- 1
- Elevation
- 7,680 ft
- Best months
- April to October
Sweetwater agate is Wyoming's signature agate, and the Sweetwater River drainage is the classic field area tied to the Granite Mountains source terrain. WSGS publications describe Sweetwater material among the state's better-known agates, while BLM rules make casual surface collecting possible on open public parcels when claims and ownership are checked first. Reported finds include agate. Below: coordinates, access notes, nearby spots, and trip-planning links.
Plan your visit
Permission required before collecting
- County
- Fremont County
- State
- Wyoming
- Coordinates
- 42.44731, -108.99584
Coordinates are approximate. Confirm the exact ground in the RockHoundR app, where land overlays show which agency manages the area.
Land & collecting status
Permission required before collecting
Requires landowner or agency permission before any collecting. Do not enter without explicit authorization.
Access note: BLM-managed public land is common in the Sweetwater drainage, but collectors should confirm surface ownership and active mining claims before collecting.
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 Sweetwater River
Comfortable months (45 to 90°F highs)
Best months: April to October. Typical highs run 78°F in midsummer and 29°F in midwinter, with winter lows near 3°F. At about 7,680 ft, snow can block access from late fall well into spring, so check conditions outside of summer.
Climate normals: NOAA 1991-2020 monthlies, SOUTH PASS CITY station (10 mi away), adjusted for elevation.
Geology at Sweetwater River
This spot sits on ground mapped as volcanic, sandstone, and conglomerate 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.
- Age
- 56–23 Ma (Eocene to Oligocene)
- Rock types
- volcanic, sandstone, and conglomerate
- Elevation
- 7,680 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.
Today's weather
Is today a good day to go?
The app shows live weather, recent rain, and a daily rockhounding score for Sweetwater River.
Get the appSources & 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:
- BLM Wyoming
- Wyoming State Geological Survey
- Fossil Butte National Monument
- Community submissions reviewed against published agency rules
Found at Sweetwater River
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 Sweetwater River.
- South PassFremont County, Wyoming · 7 mi awayBanded Iron Formation
- Fremont CountyFremont County, Wyoming · 7 mi awayAgate, Chalcedony, Jasper
- South Pass CityFremont County, Wyoming · 12 mi awayGold
- Atlantic CityFremont County, Wyoming · 14 mi awayAgate, Chalcedony, Gold
- LanderFremont County, Wyoming · 28 mi awayAgate, Jasper, Nephrite
- FarsonSweetwater County, Wyoming · 29 mi awayAgate, Chalcedony, Chert
- Eden ValleySweetwater County, Wyoming · 33 mi awayPetrified Wood
- Steamboat MountainSweetwater County, Wyoming · 34 mi awayAgate, Chalcedony, Jasper
Sweetwater River FAQ
Where is Sweetwater River?+
What rocks and minerals can you find at Sweetwater River?+
Is collecting allowed at Sweetwater River?+
What tools should I bring to Sweetwater River?+
When is the best time to visit Sweetwater River?+
How do I get to Sweetwater River?+
More rockhounding in Wyoming
See all 92 Wyoming spots →
Open Sweetwater River on the map
Use the RockHoundR app for live land overlays, weather, geology, directions, and saved finds.
