Terlingua: Calcite & Calomel Rockhounding in Brewster County, Texas

Plan your visit

Generally open to casual rockhounding

County

Brewster County

State

Texas

Nearest road

FM 170

Coordinates

29.30886, -103.62752

Coordinates are approximate. Confirm the exact ground in the RockHoundR app, where land overlays show which agency manages the area.

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.

Best time to visit Terlingua

Comfortable months (45 to 90°F highs)

Best months: October to April. Typical highs run 99°F in midsummer and 64°F in midwinter, with winter lows near 32°F. Summer heat here is intense, so carry more water than you think you need and work the early morning.

Climate normals: NOAA 1991-2020 monthlies, TERLINGUA station (3 mi away), adjusted for elevation.

Geology at Terlingua

This spot sits on Santa Elena Limestone, Sue Peaks Formation, Del Carmen Limestone, and Telephone Canyon Formation, undivided, mapped as limestone that formed roughly 115 to 100 million years ago. Carbonate rock like this is the classic host for lead, zinc, and fluorite mineralization, which typically follows old cavities and replacement zones.

Mapped unit

Santa Elena Limestone, Sue Peaks Formation, Del Carmen Limestone, and Telephone Canyon Formation, undivided

Age

115–100 Ma (Early Cretaceous)

Rock types

limestone

Elevation

3,030 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.

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

• Texas Parks and Wildlife Department
• Bureau of Economic Geology, Texas geology
• Big Bend National Park, Rules
• Community submissions reviewed against published agency rules