Argenta: Silver Rockhounding in Beaverhead County, Montana

Quick details

Access

Public area

County

Beaverhead County

State

Montana

Nearest road

Long John Road

Coordinates

45.30683, -112.88656

Geology at Argenta

This spot sits on Missoula Group, mapped as 0-800m(feldspathic sandstone)| 2300m(feldspathic quartzite, quartzitic sandstone)| 1500m(feldspathic quartzite)| 1000m(micaceous feldspathic quartzite, calcareous quartzite, and dolomitic quartzite) that formed roughly 1600 to 1000 million years ago. Metamorphic terrain like this commonly hosts vein and replacement mineralization, and old workings typically mark the productive zones.

Mapped unit

Missoula Group

Age

1600–1000 Ma (Mesoproterozoic)

Rock types

0-800m(feldspathic sandstone)| 2300m(feldspathic quartzite, quartzitic sandstone)| 1500m(feldspathic quartzite)| 1000m(micaceous feldspathic quartzite, calcareous quartzite, and dolomitic quartzite)

Elevation

7,020 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 Argenta

Best months: April to October. Typical highs run 77°F in midsummer and 24°F in midwinter, with winter lows near 4°F. At about 7,020 ft, snow can block access from late fall well into spring, so check conditions outside of summer.

Climate normals: NOAA 1991-2020 monthlies, DILLON 18 WSW station (12 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 Argenta

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

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