Alzada: Bentonite Rockhounding in Carter County, Montana

Updated June 2026

Alzada is a mapped rockhounding spot in Carter County, Montana. Reported finds include bentonite. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Public area
County: Carter County
State: Montana
Nearest road: MT 323
Coordinates: 45.02933, -104.40641

Geology at Alzada

This spot sits on Belle Fourche Formation, mapped as black shale and sandstone that formed roughly 100 to 94 million years ago. Sedimentary rock like this erodes unevenly, so the most productive collecting is typically along fresh cuts, badland slopes, and active drainages.

Mapped unit: Belle Fourche Formation
Age: 100–94 Ma (Late Cretaceous)
Rock types: black shale and sandstone
Elevation: 3,430 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 Alzada

Best months: April to October. Typical highs run 84°F in midsummer and 28°F in midwinter, with winter lows near 3°F.

Climate normals: NOAA 1991-2020 monthlies, ALBION 1 N station (14 mi away).

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 Alzada

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

Bentonite

Nearby rockhounding spots

Other rockhounding spots within driving distance of Alzada.

Custer CountyCuster County, Montana · 119 mi awayMontana Agate

Across the state line from Alzada

Alzada is close enough to the Montana border that the next-closest rockhounding spots are in a neighboring state. Worth knowing if you are already on the road.

Alzada FAQ

Where is Alzada?+

Alzada is in Carter County, Montana, at 45.02933, -104.40641. Nearest road: MT 323.

What rocks and minerals can you find at Alzada?+

Alzada is reported to produce Bentonite.

Is collecting allowed at Alzada?+

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 Alzada?+

A rock hammer, sturdy gloves, safety glasses, and a collecting bag cover the basics here. Add a spray bottle: wet rock shows color and pattern that dry rock hides.

When is the best time to visit Alzada?+

The most comfortable months at Alzada are April to October.

How do I get to Alzada?+

Open the directions link to navigate to 45.02933, -104.40641 in Google Maps. The nearest road is MT 323.

More rockhounding in Montana

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Open Alzada on the map

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