Lake Lucero

Lake Lucero is a dry playa in the southwest corner of Alkali Flat, and the two are the main source of gypsum for White Sands' dunes. A ranger-led walk brings you down to exposed selenite crystals, the clear crystal form of gypsum. This is the stop for seeing where the sand comes from; it isn't a drive-up lake. The bed is usually dry, but water can collect after abundant rain or snow.

From the trailhead, the route is 1.5 miles round trip over rough, unmaintained desert terrain and washes. It drops through a gully toward the playa, then climbs gently back to the cars. Loose soil and uneven footing make it a moderate walk. Closed-toe shoes are required. It isn't wheelchair- or stroller-accessible, and the remote route isn't a good fit for people with mobility or health concerns, infants, or very young children. Carry water and snacks and bring sun protection; rangers don't have extra water. There are no restrooms at the trailhead, though a portable toilet may be available outside the gate.

During the wetter last Ice Age, about 24,000 to 12,000 years ago, rain and snowmelt carried gypsum from the San Andres Mountains to the west and the Sacramento Mountains to the east. It collected in Lake Otero, a lake of roughly 1,600 square miles. As the climate dried about 12,000 years ago, Otero evaporated into a playa—a dry lakebed that can temporarily fill—and left concentrations of selenite. Lake Lucero is part of that present-day playa landscape, not the ancient lake itself.

Gypsum-rich water rises through the mud, where selenite forms below the playa's surface. Wind strips away clay and silt, exposing the crystals; freezing and thawing break them into smaller pieces. The fragments become sand, and wind carries the grains northeast in short bounces, a process called saltation. Lake Lucero and Alkali Flat still supply new dunes, though on a much smaller scale than in Lake Otero's time. Scratches on the grains scatter white light; right after rain, the dunes can look tan until sun and wind dry them again.

The tour passes exposed crystals in the gullies and on the lakebed. After heavy rain, shallow water can draw black-necked stilts and American avocets hunting larvae and pupfish, but don't count on water or birds every visit. For photos, wait until the ranger signals that the group is on park property; photography is prohibited on the missile range. Leave all crystals where they are—taking them is prohibited.