Mathis: Moss Agate Rockhounding in San Patricio County, Texas

Updated June 2026

Mathis is a mapped rockhounding spot in San Patricio County, Texas. Reported finds include moss agate. Below: coordinates, access notes, nearby spots, and trip-planning links.

Quick details

Access: Public area
County: San Patricio County
State: Texas
Nearest road: South State Highway 359
Postcode: 78368
Coordinates: 28.03829, -97.85979

Geology at Mathis

This spot sits on Alluvium, mapped as fine alluvium and coarse alluvium that formed within roughly the last 12,000 years. Gravels like these concentrate whatever survives the river: agate, jasper, and other tough silica typically show up as rounded, waxy stones.

Mapped unit: Alluvium
Age: < 1 Ma (Holocene)
Rock types: fine alluvium and coarse alluvium
Elevation: 60 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 Mathis

Best months: September to May. Typical highs run 95°F in midsummer and 66°F in midwinter, with winter lows near 45°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, MATHIS 4 SSW station (1 mi away).

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

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

Found at Mathis

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

Moss Agate Encyclopedia →

Nearby rockhounding spots

Other rockhounding spots within driving distance of Mathis.

Mathis FAQ

Where is Mathis?+

Mathis is in San Patricio County, Texas, at 28.03829, -97.85979. Nearest road: South State Highway 359.

What rocks and minerals can you find at Mathis?+

Mathis is reported to produce Moss Agate.

Is collecting allowed at Mathis?+

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 Mathis?+

Most agate and jasper is surface float: bring a spray bottle, a pick or small shovel, and a sturdy bag. Wet stones show their banding and translucence.

When is the best time to visit Mathis?+

The most comfortable months at Mathis are September to May. Summer heat here is intense, so carry more water than you think you need and work the early morning.

How do I get to Mathis?+

Open the directions link to navigate to 28.03829, -97.85979 in Google Maps. The nearest road is South State Highway 359.

More rockhounding in Texas

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Open Mathis on the map

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