Gem Mountain Sapphire Mine: Rockhounding in Granite County, Montana

Quick details

Access

Paid / fee dig

County

Granite County

State

Montana

Coordinates

46.24680, -113.59170

Geology at Gem Mountain Sapphire Mine

This spot sits on Surficial deposits, mapped as sand and gravel that formed within roughly the last 3 million years. Loose deposits like these are float-collecting ground: erosion keeps moving durable rocks and minerals into gravel bars, cutbanks, and washes.

Mapped unit

Surficial deposits

Age

3 Ma to present (Pleistocene to Holocene)

Rock types

sand and gravel

Elevation

5,600 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 Gem Mountain Sapphire Mine

Best months: March to October. Typical highs run 80°F in midsummer and 35°F in midwinter, with winter lows near 14°F.

Climate normals: NOAA 1991-2020 monthlies, PHILIPSBURG RS station (15 mi away), adjusted for elevation.

Land & collecting status

Pay-to-dig site

This is a fee-dig location. Hours, prices, and what you can keep vary by operator. Call ahead before driving out.

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