Gem Mountain: Sapphire Rockhounding in Madison County, Montana

Updated June 2026

Gem Mountain is a mapped rockhounding spot in Madison County, Montana. Reported finds include sapphire. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Paid / fee dig
County: Madison County
State: Montana
Coordinates: 45.34300, -112.35600

Geology at Gem Mountain

This spot sits on Bozeman Group and related valley-fill deposits, undivided, mapped as tuffaceous sandstone and siltstone that formed roughly 56 to 3 million years ago. Volcanic ground like this weathers into rocky slopes and float, and fresh exposures in cuts and drainages are usually the most productive places to look.

Mapped unit: Bozeman Group and related valley-fill deposits, undivided
Age: 56–3 Ma (Eocene to Pliocene)
Rock types: tuffaceous sandstone and siltstone
Elevation: 5,430 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 Gem Mountain

Best months: April to October. Typical highs run 81°F in midsummer and 31°F in midwinter, with winter lows near 12°F.

Climate normals: NOAA 1991-2020 monthlies, DILLON AP station (11 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

Found at Gem Mountain

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

Sapphire Encyclopedia →

Nearby rockhounding spots

Other rockhounding spots within driving distance of Gem Mountain.

Across the state line from Gem Mountain

Gem Mountain 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.

Gem Mountain FAQ

Where is Gem Mountain?+

Gem Mountain is in Madison County, Montana, at 45.34300, -112.35600.

What rocks and minerals can you find at Gem Mountain?+

Gem Mountain is reported to produce Sapphire.

Is collecting allowed at Gem Mountain?+

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. Always confirm current rules with the managing agency before a trip.

What tools should I bring to Gem Mountain?+

A rock hammer, a sieve, and a small shovel work well for garnet-type minerals, which concentrate as resistant grains in soils and creek gravels.

When is the best time to visit Gem Mountain?+

The most comfortable months at Gem Mountain are April to October.

How do I get to Gem Mountain?+

Open the directions link to navigate to 45.34300, -112.35600 in Google Maps. Some spots are remote, so check road conditions before driving out.

More rockhounding in Montana

See all 87 Montana spots →

Open Gem Mountain on the map

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