Which desert contains the world's largest gypsum dune field (White Sands)?

The Chihuahuan Desert contains White Sands, the world’s largest gypsum dune field.

White Sands lies in New Mexico’s Tularosa Basin, an enclosed depression within the Chihuahuan Desert. The dunes are made not of ordinary quartz sand but of gypsum, a soft mineral also known as calcium sulfate. Because gypsum usually dissolves in water, large exposed gypsum dunes are exceptionally rare.

The field developed as water dissolved gypsum from surrounding mountains and carried it into the basin. Ancient Lake Otero later evaporated, leaving selenite crystals behind. Wind broke those crystals into fine grains and pushed them into the brilliant white dunes seen today. This mineral cycle continues through rainfall, groundwater, evaporation, and wind.

White Sands became a national monument in 1933 and a national park in 2019. The park protects only part of the roughly 275-square-mile dunefield; the rest lies within White Sands Missile Range. Visitors often confuse the site with Great Sand Dunes in Colorado, whose dunes are primarily composed of quartz-rich sand.