Mariscal Mine

When access is open, the easiest route is about 22 miles along primitive River Road East from just west of Rio Grande Village. The National Park Service advises a high-clearance vehicle with at least 8 inches of clearance; after rain, four-wheel drive is required. Expect a rough, isolated drive and a steep walk over loose, uneven ground between parts of the site. Allow at least half a day, and carry water and a good spare as the park advises for primitive roads.

Cinnabar ore was heated in retorts and furnaces until mercury vapor could be carried through iron pipes into condensers and cooled back into liquid. The Scott Furnace, built from local Pen clay bricks, stood about 20 feet square and 40 feet high. Across the mine’s 1900–1943 operating life, it produced 1,400 flasks of mercury, each weighing 76 pounds, nearly a quarter of U.S. output.

The mine employed 20 to 40 people from 1919 to 1923. Many were Mexican citizens who had crossed into Texas to escape the Mexican Revolution, and their families kept gardens near Fresno Creek. The scattered one-to-three-room home ruins make this more than a collection of machinery: you can see the remains of the settlement that supported the work. A later company built ten concrete-and-stucco houses in 1942–43, likely never occupied.

The National Park Service warns that furnace and condenser materials and mine tailings may contain poisonous mercury. Don’t touch or collect material, climb the fragile structures, or approach mine shafts; some openings may not be fenced. A ruined-home window frames Pummel Peak, a striking way to connect the buildings to the surrounding mountains if you can see it from safe ground without touching or climbing the walls.