Green Mountain: Banded Agate & Moss Agate Rockhounding in Fremont County, Wyoming

Quick details

Access

Public area

County

Fremont County

State

Wyoming

Nearest road

Green Mountain Road

Coordinates

42.35736, -107.72365

Geology at Green Mountain

This spot sits on ground mapped as Crooks Gap Conglomerate that formed roughly 66 to 3 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

Crooks Gap Conglomerate

Age

66–3 Ma (Tertiary)

Elevation

8,520 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 Green Mountain

Best months: April to October. Typical highs run 77°F in midsummer and 23°F in midwinter, with winter lows near 1°F. At about 8,520 ft, snow can block access from late fall well into spring, so check conditions outside of summer.

Climate normals: NOAA 1991-2020 monthlies, JEFFREY CITY station (11 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 Green Mountain

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

• Banded AgateEncyclopedia →
• Moss AgateEncyclopedia →
• Aventurine
• GarnetEncyclopedia →
• SapphireEncyclopedia →