Big Horn River: Dry Head Agate Rockhounding in Big Horn County, Wyoming
Updated July 2026
Big Horn River is a mapped rockhounding spot in Big Horn County, Wyoming. Reported finds include dry head agate. Below: coordinates, access notes, nearby spots, and trip-planning links.
Map showing Big Horn River in Big Horn County, Wyoming
Quick details
- Access
- Permission required
- County
- Big Horn County
- State
- Wyoming
- Nearest road
- Mouth of the Canyon Trail
- Coordinates
- 44.96434, -108.25090
Geology at Big Horn River
This spot sits on Tensleep Sandstone and Amsden Formation, mapped as sandstone, dolostone, and shale that formed roughly 360 to 250 million years ago. Chert and agate nodules typically form inside carbonate rock like this and weather out as tough, waxy lumps in soils and creek beds.
- Mapped unit
- Tensleep Sandstone and Amsden Formation
- Age
- 360–250 Ma (Mississippian to Permian)
- Rock types
- sandstone, dolostone, and shale
- Elevation
- 3,910 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 Big Horn River
Best months: March to October. Typical highs run 86°F in midsummer and 31°F in midwinter, with winter lows near 7°F.
Climate normals: NOAA 1991-2020 monthlies, LOVELL station (12 mi away).
Land & collecting status
Permission required before collecting
Requires landowner or agency permission before any collecting. Do not enter without explicit authorization.
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:
- BLM Wyoming
- Wyoming State Geological Survey
- Fossil Butte National Monument
- Community submissions reviewed against published agency rules
Found at Big Horn River
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 Big Horn River.
- LovellBig Horn County, Wyoming · 14 mi awayGypsum, Fossils
- LovellBig Horn County, Wyoming · 15 mi awayFossils, Ammonites, Dinosaur Bones
- GreybullBig Horn County, Wyoming · 31 mi awayGastroliths, Petrified Dinosaur Bone, Fossils
- Red GulchBig Horn County, Wyoming · 37 mi awayGypsum
- Cedar MountainPark County, Wyoming · 54 mi awayTravertine
- Rattlesnake MountainPark County, Wyoming · 57 mi awayAnhydrite
- HyattvilleBig Horn County, Wyoming · 61 mi awayGypsum, Dinosaur Bones, Gastroliths
- MeeteetsePark County, Wyoming · 65 mi awayAgate, Jasper
Across the state line from Big Horn River
Big Horn River 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.
- Bear CanyonCarbon County, Montana · 16 mi awayGeode, Agate
- Pryor MountainsTop pick in MontanaBig Horn County, Montana · 19 mi awayFossils, Agate, Chalcedony
- Big Horn CanyonBig Horn County, Montana · 28 mi awayAgate, Chalcedony, Jasper
- FrombergCarbon County, Montana · 44 mi awayCoal, Pyrite
- Yellowstone River (Billings area)Top pick in MontanaYellowstone County, Montana · 65 mi awayMontana Agate, Chalcedony, Chert
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More rockhounding in Wyoming
See all 82 Wyoming spots →Open Big Horn River on the map
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