South Boulder River: Quartz Rockhounding in Madison County, Montana

Updated June 2026

South Boulder River is a mapped rockhounding spot in Madison County, Montana. Reported finds include quartz. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Public area
County: Madison County
State: Montana
Nearest road: South Boulder Road
Coordinates: 45.72625, -111.97468

Geology at South Boulder River

This spot sits on Three Forks and Jefferson Formations, mapped as limestone, shale, and dolostone that formed roughly 370 to 345 million years ago. Carbonate rock like this dissolves and weathers readily, so fresh road cuts, quarries, and creek exposures are typically the most productive ground.

Mapped unit: Three Forks and Jefferson Formations
Age: 370–345 Ma (Late Devonian to Mississippian)
Rock types: limestone, shale, and dolostone
Elevation: 5,350 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 South Boulder River

Best months: March to October. Typical highs run 82°F in midsummer and 33°F in midwinter, with winter lows near 10°F.

Climate normals: NOAA 1991-2020 monthlies, TWIN BRIDGES station (21 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 Montana — Recreational mineral collecting
Montana Bureau of Mines and Geology
Gem Mountain Sapphire Mine (fee-dig operator)
Community submissions reviewed against published agency rules

Found at South Boulder River

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

Quartz Encyclopedia →

Nearby rockhounding spots

Other rockhounding spots within driving distance of South Boulder River.

South Boulder River FAQ

Where is South Boulder River?+

South Boulder River is in Madison County, Montana, at 45.72625, -111.97468. Nearest road: South Boulder Road.

What rocks and minerals can you find at South Boulder River?+

South Boulder River is reported to produce Quartz.

Is collecting allowed at South Boulder River?+

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 South Boulder River?+

A rock hammer, a small pry bar, gloves, and safety glasses cover most crystal ground. A screen helps in loose pocket soil, and newspaper protects points on the way out.

When is the best time to visit South Boulder River?+

The most comfortable months at South Boulder River are March to October.

How do I get to South Boulder River?+

Open the directions link to navigate to 45.72625, -111.97468 in Google Maps. The nearest road is South Boulder Road.

More rockhounding in Montana

See all 87 Montana spots →

Open South Boulder River on the map

Use the RockHoundR app for live land overlays, weather, geology, directions, and saved finds.