Tin Mountain: Fluorapatite & Quartz Rockhounding in Custer County, South Dakota

Updated June 2026

Tin Mountain is a mapped rockhounding spot in Custer County, South Dakota. Reported finds include fluorapatite, quartz, almandine garnet, cassiterite, mica, and more. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Public area
County: Custer County
State: South Dakota
Nearest road: Warren Gulch
Coordinates: 43.75574, -103.72009

Geology at Tin Mountain

This spot sits on ground mapped as Distal metagraywacke that formed roughly 2500 to 1600 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: Distal metagraywacke
Age: 2500–1600 Ma (Paleoproterozoic)
Elevation: 5,780 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 Tin Mountain

Best months: April to October. Typical highs run 78°F in midsummer and 34°F in midwinter, with winter lows near 14°F.

Climate normals: NOAA 1991-2020 monthlies, CUSTER CO AP station (5 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.

Sources: RockHoundR public spot dataset, app land overlays, and local agency review before each trip.

Found at Tin Mountain

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

Nearby rockhounding spots

Other rockhounding spots within driving distance of Tin Mountain.

Across the state line from Tin Mountain

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

Tin Mountain FAQ

Where is Tin Mountain?+

Tin Mountain is in Custer County, South Dakota, at 43.75574, -103.72009. Nearest road: Warren Gulch.

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

Tin Mountain is reported to produce Fluorapatite, Quartz, Almandine Garnet, Cassiterite, Mica, Tourmaline, Zircon.

Is collecting allowed at Tin Mountain?+

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 Tin Mountain?+

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 Tin Mountain?+

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

How do I get to Tin Mountain?+

Open the directions link to navigate to 43.75574, -103.72009 in Google Maps. The nearest road is Warren Gulch.

More rockhounding in South Dakota

See all 43 South Dakota spots →

Open Tin Mountain on the map

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